Dissertations / Theses: 'GaAs:Mn'

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González, Balanta Miguel Ángel 1985. "Interação entre portadores e íons magnéticos em poços quânticos de InGaAs/GaAs:Mn." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/276965.

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Orientador: Maria José Santos Pompeu Brasil Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin Made available in DSpace on 2018-08-25T21:17:06Z (GMT). No. of bitstreams: 1 GonzalezBalanta_MiguelAngel_D.pdf: 5068966 bytes, checksum: c4aafc0a3e660efae9cc987f6dd987e5 (MD5) Previous issue date: 2014 Resumo: Neste trabalho investigamos a interação entre portadores confinados em poços quânticos de InGaAs/GaAs e íons de Mn de uma dopagem tipo delta na barreira do poço. Utilizamos como base para este estudo dois tipos de estruturas. O primeiro tipo tem apenas a dopagem tipo delta de Mn e o segundo tipo, inclui duas camadas de dopagem tipo delta nas duas barreiras do poço, sendo uma dopagem de C e a outra de Mn. Observamos que a assimetria das estruturas devido às dopagens se reflete na interação dos portadores confinados com os íons de Mn. Os resultados indicam que esta interação se torna relativamente mais forte no conjunto de amostras com dopagem assimétrica apenas de Mn. Em nossa investigação, utilizamos diversas técnicas ópticas como fotoluminescência, fotoluminescência de excitação e fotoluminescência resolvida no tempo, incluindo análises da polarização da luz emitida e efeitos de campo magnético. Apesar da separação espacial entre os íons de Mn e os portadores confinados no poço, observamos vários efeitos que associamos a interação entre estas entidades. Observamos uma significativa amplificação da intensidade da força de oscilador de transições proibidas do poço em estruturas dopadas apenas com Mn. Este efeito foi interpretado como uma possível indicação da formação de polarons magnéticos ligados. Nas medidas com campo magnético, vimos que o grau de polarização dos portadores apresenta uma componente associada à presença dos íons de Mn. Esta componente, dominante apenas a baixos campos magnéticos, segue uma função tipo Brillouin associada a sistemas ferromagnéticos. Dependendo do perfil da estrutura, esta componente pode ter seu sinal invertido, levando a uma dependência da polarização com o campo magnético anômala. Finalmente, realizamos um estudo detalhado da dinâmica de polarização dos portadores com medidas de fotoluminescência resolvida no tempo. Desenvolvemos uma técnica especial envolvendo dois feixes de laser pulsados com controle tanto da separação temporal entre seus pulsos, quanto das suas polarizações circulares, que podiam ser iguais ou invertidas. Observamos que o grau de polarização gerado por um pulso é alterado se logo antes dele (centenas de pico-segundos), a amostra é excitada com pulso com polarização invertida. Associamos este efeito a um tipo de memória de polarização relacionada com a magnetização óptica dos íons de Mn. Assim, a excitação com luz circularmente polarizada gera portadores com spin preferencial, que atuam sobre os íons magnéticos, e que por sua vez afetam a polarização dos próprios portadores, agindo como um reservatório de polarização devido aos tempos de spin relativamente mais longos dos íons de Mn. Notamos que os efeitos mencionados acima são consideravelmente mais fortes no conjunto de amostras apenas com dopagens de Mn que devem apresentar um perfil de potencial mais assimétrico. Também obtivemos resultados consistentes que demonstram que estes efeitos tendem a diminuir quando a quantidade de Mn na camada delta é reduzida, quando a separação entre a camada delta de Mn e o poço quântico é aumentada, e quando aumentamos a temperatura do sistema. Em especial, os efeitos tendem a desaparecer para temperaturas em torno de 60 K, consistente com os valores da temperatura de Curie obtida para amostras similares Abstract: In this work we investigated the interaction between confined carriers in of InGaAs/GaAs quantum wells (QWs) and Mn ions from a Mn delta-doping at the barrier of the QW. We have used two types of structures in this study. Samples of the first type have only a Mn delta-doping at the QW barrier, while samples from the second type include an additional C delta-doping layer at the other barrier. We found that the asymmetry of the structures due to doping is reflected in the interaction of carriers confined in the well and the Mn ions. The results indicate that this interaction becomes relatively stronger in the set of samples with asymmetrical doping of Mn solely. In our research, we have performed continuous-wave photoluminescence (CW-PL), excitation photoluminescence (CW-PLE), time-resolved photoluminescence (TR-PL), including analysis of the polarization of the emitted light and effects of a magnetic field. Despite the spatial separation between the Mn ions and the carriers confined in the QW, we observed various effects attributed to the interaction between these entities. We observed a significant enhancement of the intensity of the oscillator strength from transitions that are prohibited for symmetric QWs for the Mn doped structures. This effect was interpreted as a possible indication of the formation of bound magnetic polarons (BMP). In the measurements under a magnetic field, we observed that the degree of polarization of the carrier has a component associated with the presence of Mn ions. This component dominates the polarization under small magnetic fields and follows a like-Brillouin function associated to ferromagnetic systems. Depending on the profile of the structure, this component may have its sign reversed, leading to an anomalous polarization dependency with magnetic field. Finally, we performed a detailed study of the dynamics of the polarization of the carriers with time-resolved photoluminescence. We have developed a special technique involving two pulsed beams with a variable time-delay and individually-controlled circular-polarizations, which could be equal or reversed. We observed that the degree of polarization generated by a pulse is changed if just before it (hundreds of pico seconds) the sample was excited with a pulse with reversed polarization. We associated this effect to a kind of polarization memory related to the optical magnetization of Mn ions. Therefore, the excitation with circularly-polarized light generates carriers with a preferential spin that might act on the magnetic ions. In turn, the polarized Mn ions must affect the spin-polarization of the carriers, acting as a reservoir of the polarization, due to the relatively longer spin times of the Mn ions. We noticed that all these effects are considerably stronger for the set of samples doped only with Mn, that should present a more asymmetric potential profile. We also obtained consistent results revealing that all these effects tend to decrease when the amount of Mn in the delta-layer is reduced, when the separation between the Mn layer and the QW is increased, and when we increase the temperature of the sample. In particular, the effects tend to disappear at temperatures around 60 K, in accordance with the Curie temperature found for similar samples Doutorado Física Doutor em Ciências

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Khazen, Khashayar. "Etude des couches Nanométriques de GaMnAs par Résonance Ferromagnétique." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2008. http://tel.archives-ouvertes.fr/tel-00329331.

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Cette thèse est consacrée à l'étude par Résonance Ferromagnétique (RFM) de l'influence des contraintes et des concentrations en trous et en Mn, sur les propriétés magnétiques de films nanométriques de Ga1-xMnxAs. L'influence des contraintes a été étudié dans des films contenant 7% de Mn déposés sur GaAs ou GaInAs et contraints en compression ou en extension respectivement. Les axes de facile aimantation, le type d'anisotropie, le facteur de Landé, la température de Curie et les constantes d'anisotropie on été déterminés par RFM. La passivation par l'hydrogène de l'activité électrique des Mn a permis l'étude de l'influence de la concentration en trous dans ces systèmes. Différents régimes de conductivité ont pu être atteints: isolant, conduction par bande d'impureté et métallique. Les facteurs g dépendent à la concentration de trous et la température. La relation théorique entre ces facteurs et la polarisation de trous est présentée. Les variations des constantes d'anisotropie magnétocrystallines sont comparées aux modèles théoriques. La plus faible concentration en trous permettant d'atteindre un état ferromagnétique est estimée à 1019cm-3. La structure des domaines a été étudiée par microscopie magnéto-optique pour cette concentration. L'influence du niveau de dopage en Mn a été étudiée dans la plage de 7% à 21%. Les résultats montrent que, contrairement aux prédictions du modèle de champ moyen, la température de Curie ne dépasse pas 180K même pour les forts dopages, ce qui est attribué à un haut niveau de compensation magnétique. Enfin, la relaxation de l'aimantation est étudiée et des facteurs de damping anisotropes sont mis en évidence.

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Vijarnwannaluk, Sathon. "Optical studies of GaAs:C grown at low temperature and of localized vibrations in normal GaAs:C." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/27491.

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Optical studies of heavily-doped GaAs:C grown at low temperature by molecular beam epitaxy were performed using room-temperature photoluminescence, infrared transmission, and Raman scattering measurements. The photoluminescence experiments show that in LT-GaAs:C films grown at temperatures below 400 °C, nonradiative recombination processes dominate and photoluminescence is quenched. When the growth temperature exceeds 400 °C, band-to-band photoluminescence emission appears. We conclude that the films change in character from LT-GaAs:C to normal GaAs:C once the growth temperature reaches 400 °C. Annealing, however, shows a different behavior. Once grown as LT-GaAs:C, this material retains its nonconducting nonluminescing LT characteristics even when annealed at 600 °C. The Raman-scattering measurements showed that the growth temperature and the doping concentration influence the position, broadening, and asymmetry of the longitudinal-optical phonon Raman line. We attribute these effects to changes in the concentration of interstitial carbon in the films. Also, the shift of the Raman line was used to estimate the concentration of arsenic-antisite defects in undoped LT-GaAs. The infrared transmission measurements on the carbon-doped material showed that only a fraction of the carbon atoms occupy arsenic sites, that this fraction increases as the growth temperature increases, and that it reaches about 100% once the growth temperature reaches 400 °C. The details of all these measurements are discussed. Infrared transmission and photoluminescence measurements were also carried out on heavily-doped GaAs:C films grown by molecular beam epitaxy at the standard 600 C temperature. The infrared results reveal, for dopings under 5 x 10⁹ cm⁻³, a linear relation between doping concentration and the integrated optical absorption of the carbon localized-vibrational-mode band. At higher dopings, the LVM integrated absorption saturates. Formation of CAs-CAs clusters is proposed as the mechanism of the saturation. The photoluminescence spectra were successfully analyzed with a simple model assuming thermalization of photoelectrons to the bottom of the conduction band and indirect-transition recombination with holes populating the degenerately doped valence band. The analysis yields the bandgap reduction and the Fermi-level-depth increase at high doping. Ph. D.

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Person, Patrice. "Influence de l'enrichissement superficiel en arsenic sur l'ohmicité du contact n-GaAs:In\Au." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb376088413.

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Person, Patrice. "Influence de l'enrichissement superficiel en arsenic sur l'ohmicité du conact n-GaAs:In\Au." Ecully, Ecole centrale de Lyon, 1987. http://www.theses.fr/1987ECDL0009.

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Presentation des differents modeles de jonctions metal-semiconducteur et explication des mecanismes de transport du courant a l'interface. On definit alors le contact ohnique et la resistance specifique de contact. On conclue quand a la faisabilite de contacts ohniques de bonne qualite apres enrichissement de la surface du substrat de n-gaas en arsenic

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Songprakob, Wantana. "Optical studies of highly-doped GaAs:C." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/28927.

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Infrared reflectivity and transmittance measurements (200=5000 cm^-1) were carried out on heavily-doped GaAs:C films grown by molecular beam epitaxy. With increasing carbon concentration, a broad reflectivity minimum develops in the 1000=3000 cm^-1 region and the one-phonon band near 270 cm^-1 rides on a progressively increasing high-reflectivity background. An effective-plasmon/one-phonon dielectric function with only two free parameters (plasma frequency Ï p and damping constant Î³p) gives a good description of the main features of the reflectivity spectra. The dependence of effective plasma frequency on hole concentration p is linear. At each doping, the effective-plasmon damping constant is large and corresponds to an optical hole mobility that is about half the Hall mobility at that p. Secondary-ion mass spectroscopy and localized-vibrational-mode measurements indicate that the Hall-effect-derived hole concentration is close to the carbon concentration and that the Hall factor is close to unity, so that the Hall mobility provides a good estimate of the actual dc mobility. Also, analysis shows that, for our highly-doped samples, the observed dichotomy between the dc and infrared mobilities is not a statistical-averaging artifact of the approximations involved in the model. The explanation of the small infrared mobility resides in the influence of intervalence band absorption on the effective-plasmon fit, which operationally defines that mobility via the effective-plasmon damping. The optical properties obtained with the use of the effective-plasmon model for GaAs:C yield a phenomenological, approximate, overall picture of the infrared spectra. But the neglect of intervalenceband transitions, for this p-type semiconductor, is shown (in this dissertation) to be a serious drawback of this simple model. In order to obtain the optical properties of GaAs:C in a model-independent way, and to attempt to resolve the apparent dc/infrared mobility dichotomy, we made use of a recently-developed spectroscopic-analysis procedure. Using direct numerical-solution techniques for the reflectance (R) and transmittance (T) equations of a multilayer structure, we analyzed our infrared R and T results for highly-doped films having hole concentrations from 2Ã 10^19 up to 1.4Ã 10^20 cm^-3. The optical properties were determined for photon energies from 0.07 to 0.6 eV, in which region plasmon (intraband) and intervalenceband contributions are in competition. Our results for the optical absorption coefficient resolve two separate peaks located (at high doping) at about 0.1 and 0.2 eV. (The effective-plasmon model necessarily missed the two-peak character of the actual absorption spectrum.) By carrying out theoretical calculations of the intervalenceband (IVB) absorption processes for our dopings, we identify the peak near 0.2 eV with light-hole to heavy-hole IVB transitions, and we attribute the lower-energy peak to the hole plasmon. Our experimental absorption spectra are very well described by a model combining the intervalenceband contribution to the dielectric function with a plasmon contribution. The hole-plasmon parameters omega_plasmon and gamma_plasmon that we obtain for highly-doped p-GaAs yield an infrared mobility which (unlike the too-small IVB-entangled infrared mobility implied by the use of the usual effective-plasmon model) is in substantial agreement with the dc mobility. Therefore, in actuality, there is no dc/infrared mobility discrepancy. The discrepancy implied by the use of the usual, standard-operating-procedure, effective-plasmon model is a consequence of the inadequacy of that model for p-type semiconductors exhibiting intervalenceband infrared absorption. Raman-scattering measurements were carried out on the GaAs:C films. Only the phononlike coupled plasmon-phonon mode is observed. The non-occurrence of the plasmonlike mode is due to the large damping of the hole plasmon and the competition with strong Raman scattering by intervalenceband transitions among the heavy-hole, light-hole, and split-off bands. Analysis of the phononlike coupled mode, within the framework of the wavevector-dependent Lindhard-Mermin dielectric function, supports the hole properties that we determined by Hall and infrared studies. Photoluminescence measurements showed that the split-off band also participates in the photoluminescence of GaAs:C, giving rise to an above-bandgap emission band corresponding to transitions from the conduction band to the split-off valence band. Ph. D.

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Hamamdjian, Gilbert. "Fluctuations de potentiel et conductivité mixte dans GaAs:Cr semi-isolant." Montpellier 2, 1987. http://www.theses.fr/1987MON20003.

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Realisation de mesures de conductivite continue, de conductivite alternative haute frequence, de pouvoir thermoelectrique, entre 300 et 450 k. En developpant un modele tenant compte des fluctuations de potentiel a longue portee, il est montre qu'il est possible d'envisager toutes les situations physiques possibles dans le compose semi-isolant et de rendre compte de tous les comportements experimentaux

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Khoukh, Abdelaziz. "GaAs et GaAs:In influence des traitements de surface et caractérisation de l'homogénéité par imagerie de la photoluminescence /." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37614697d.

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Mendonça, Cesar Augusto Curvello de. "Caracterização ótica de epitaxia MBE de GaAs e exciton ligado ao aceitador de estanho em LPE-GaAs:Sn." [s.n.], 1987. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277717.

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Orientador: Eliermes Arraes Meneses Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin Made available in DSpace on 2018-07-14T21:40:07Z (GMT). No. of bitstreams: 1 Mendonca_CesarAugustoCurvellode_M.pdf: 1779771 bytes, checksum: d1a5e39ca7e4da8c9f3213d9f403a4db (MD5) Previous issue date: 1987 Resumo: Foram feitas medidas de fotoluminescência em regime de baixo nível de excitação ótica e baixas temperaturas (< 2K). Os objetivos deste trabalho foram a caracterização e o estudo de algumas amostras de Arseneto de Gálio(GaAs), crescidas por Epitaxia por Feixe Molecular(MBE) não dopadas, e outras crescidas por Epitaxia de Fase Líquida(LPE) dopadas com Estanho(Sn). Nas primeiras, a baixa eficiência quântica de emissão das linhas excitônicas foram associadas à possível existência de grande concentração de defeitos gerados no processo de crescimento. Por outro lado, observamos alta Intensidade para linhas atribuídas a transições envolvendo impurezas aceitadoras, as quais apontaram para a presença de altas concentrações de Carbono no material. Nas últimas verificamos, através do espectro, a presença de impurezas aceitadoras de Zinco, Carbono e Estanho. Focalizamos principalmente o nível aceitador profundo introduzido no "gap" do GaAs, pelo Sn, através das transições ocorridas a partir do complexo exciton ligado à impureza (Snº, X) e banda impureza (e, Snº). Um cálculo para energia de ligação do complexo foi proposto, considerando-se uma renormalização dos valores da massa efetiva de buraco, m*b, e da constante dielétrica Abstract: Photoluminescence measurements have been performed under low excitation levels and low temperatures (< 2K). The main goals in this work has been the characterization and the study of some samples of undoped Gallium Arsenide (GaAs), grown in a Molecular Bean Epitaxy (MBE) system, and Liquid-Phase-Epitaxy(LPE) GaAs, which were intentionally doped with Tin(Sn). In the former the low emission quantum efficiency of the excitonic lines has been related to the possible existence of a high concentration of defects, generated in the growth process. On the other hand, the high intensity observed in those lines attributed to transitions involving acceptor impurities, pointed to the presence of high concentrations of Carbon in this material. In the latter, the presence of acceptor impurities as Zinc, Carbon and Tin has been verified. We foccused most of our attention at the deep acceptor level, in the gap, due to Sn in GaAs through the transitions from the excitonic complex (Snº, X) and band impurity (e, Snº). A calculation of the binding energy of this complex has been proposed, taking into account a renormalization of the hole effective mass, m*h, and dielectric constant Mestrado Física Mestre em Física

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Khoukh, Abdelaziz. "GaAs & GaAs:In : Influence des traitements de surface et caractérisation de l'homogénéité par imagerie de la photoluminescence." Ecully, Ecole centrale de Lyon, 1988. http://www.theses.fr/1988ECDL0024.

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Dans ce travail, nous avons effectue une etude comparative des substrats de gaas et gaas:in pendant certains traitements technologiques (polissage, attaque chimique, recuit). Nous montrons que la procedure de polissage de gaas par une solution aqueuse de naocl ne peut-etre appliquee pour gaas:in sans modification. La vitesse de polissage croit avec la teneur en indium et la concentration optimale de naocl doit etre diminuee dans le cas de gaas:in. De plus, l'attaque chimique dans une solution de naocl permet de reveler les striations d'indium dans le materiau gaas:in. Nous avons egalement etudie la decomposition thermique des substrats non proteges de gaas:in. Nous montrons que le recuit a des temperatures proches de 700#oc provoque une exodiffusion de l'indium suivie par la nucleation d'ilots d'indium a la surface. Pour des temperatures de recuit proches de 850#oc, l'exodiffusion est suivie par une formation de precipites d'indium et de gallium pres de la surface. Dans le cadre de ce travail, nous avons aussi etudie les substrats gaas et gaas:in par imagerie de photoluminescence (pl) a temperature ambiante. Nos mesures mettent en evidence la presence d'inhomogeneites diverses dues aux dislocations et leurs structures cellulaires, aux striations de dopage, aux bandes de glissement et aux defauts de surface. Nous montrons egalement que l'intensite de pl et le contraste des images sont fortement influences par les traitements de surface (attaque, recuit, depot d'isolant). Les resultats obtenus sont discutes sur la base d'un modele theorique simple, fonde sur la resolution de l'equation de continuite

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Yun, Henry K. "Growth and characterization of GaAsN compound semiconductors /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/10614.

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Gabilliet, Sylvie. "Contribution à la construction d'une installation de croissance HGF premiers résultats sur GaAs:Nb." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb375977449.

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Thomas, Tomos Daniel. "Investigation of material and device properties of GaAsSbN for multi-junction solar cell applications." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/62904.

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Multi-junction solar cells (MJSCs) have achieved the highest solar power conversion efficiency to date of any type of solar cell and still have considerable potential for improvement compared to their theoretical efficiency. The bandgap combination of sub-cells is an extremely important factor in cell efficiency, with new materials with particular bandgaps necessary to increase efficiency further. Possible improved multi-junction solar cell designs require sub-cells with bandgaps between 1.2 and 0.8 eV. The dilute nitride alloy GaAsSbN can provide adjustable bandgaps in this region while remaining lattice-matched to common Ge and GaAs substrates. This thesis presents measurements and analysis of GaAsSbN 1 eV material and devices. Firstly, simulations of overall MJSC designs for concentrator photovoltaic applications are presented, including the importance of bandgap tunability in the 1 eV region. The material and device properties of 1 eV GaAsSbN subcells are studied experimentally and their performance compared to that necessary for inclusion in MJSCs. Electroreflectance spectroscopy and a model dielectric function are used to examine the absorption properties of GaAsSbN. Time-resolved photoluminescence spectroscopy is used to examine carrier recombination times and mechanisms, finding a typical recombination lifetime of 400 ps. Solar cell devices are electrically and optically characterised using current-voltage, capacitance-voltage and quantum efficiency measurements. The devices are modeled in order to investigate transport, finding a 30 nm hole diffusion length and 500 nm electron diffusion length. Improved sub-cell designs are proposed. Practical limits to the performance of GaAsSbN sub-cells are discussed.

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Semenzato, Marcos Jose. ""Propriedades ópticas e elétricas de filmes epitaxiais de GaAs:Si crescidos na superfície (311)A"." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-03122002-103444/.

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Um estudo sistemático de caracterização de filmes de GaAs dopados com Silício e crescidos por Epitaxia de Feixes Moleculares sobre substratos de GaAs orientados na superfície (311)A, foi desenvolvido visando compreender os mecanismos de incorporação do Si no filme. Na superfície (311)A o Si tem comportamento anfótero, ou seja, pode ocupar tanto o sítio do Ga como o do As, o que resulta em filmes com portadores tipo n e p, respectivamente. A característica elétrica do filme depende, basicamente, das seguintes condições de crescimento: i) razão entre os fluxos de Ga e As; e ii) temperatura do substrato. As técnicas de caracterização utilizadas foram fundamentalmente fototoluminescência, IxV e Efeito Hall. A partir dos filmes de GaAs:Si crescidos na superfície (311)A, foram estudadas as características elétricas de junções Metal-Semicondutor(M-SC) obtidas a partir da deposição seqüencial de AuGe/Ni e Au/Zn/Au para os filmes com características n e p respectivamente. A resistividade de contato foi estudada como função da temperatura e tempo de tratamento térmico, a partir de um sistema desenvolvido para RTA(Rapid Thermall Annealing), obtendo-se as condições ideais dos contatos no regime ôhmico. A técnica de Difração de R-X foi utilizada para verificar a evolução da microestrutura formada na interface M-SC, evidenciando a formação da fase AuGa, responsável pela característica ôhmica do contato. O estudo realizado serviu como base para o desenvolvimento de junções p-n baseadas na superfície (311)A e sua aplicação em dispositivos optoeletrônicos.

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Saha, Uttam Kumar. "Photoluminescence and kinetic of MOCVD grown P-type GaAs:Nd and Nd-implanted semi-insulating GaAs." Ohio University / OhioLINK, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1178044230.

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Covre, Felipe Soares. "Estudo das propriedades ópticas de filmes finos e poços quânticos de GaAsPN/GaPN." Universidade Federal de São Carlos, 2016. https://repositorio.ufscar.br/handle/ufscar/8411.

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Submitted by Alison Vanceto (alison-vanceto@hotmail.com) on 2017-01-03T13:08:29Z No. of bitstreams: 1 DissFSC.pdf: 3416104 bytes, checksum: 8ad6353644ccdd0f0d768fbd0ed2324f (MD5) Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2017-01-16T16:14:02Z (GMT) No. of bitstreams: 1 DissFSC.pdf: 3416104 bytes, checksum: 8ad6353644ccdd0f0d768fbd0ed2324f (MD5) Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2017-01-16T16:14:09Z (GMT) No. of bitstreams: 1 DissFSC.pdf: 3416104 bytes, checksum: 8ad6353644ccdd0f0d768fbd0ed2324f (MD5) Made available in DSpace on 2017-01-16T16:14:17Z (GMT). No. of bitstreams: 1 DissFSC.pdf: 3416104 bytes, checksum: 8ad6353644ccdd0f0d768fbd0ed2324f (MD5) Previous issue date: 2016-09-08 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Diluted nitride III-V semiconductor leagues have physical properties that make them interesting for applications on optoelectronic devices. The possibility to lattice matching GaAsPN with silicon makes this semiconductor interesting for studies. In this dissertation we investigated the optical and magneto optical properties of semiconductors nanostructures of the type GaP(N)/GaAsPN. Mesures of photoluminescence (PL), photoluminescence excitation (PLE) and magneto photoluminescence (Magneto-PL) under high fields (B≤ 15T) were performed in films of GaAsPN and multiple quantum wells (MQW) of GaAsPN/GaPN. We have studied localizations effects with measures of diamagnetic shift, stoke shift and the dependence of photoluminescence peak with temperature. We observed a negative diamagnetic shift for some samples, which is an anomalous effect in these systems. It was also seen a red shift of the PL peak when the MQW samples suffered a thermal treatment. Analyzing the spin polarization properties of this material, utilizing magneto photoluminescence resolved with circular polarization, we observed polarization of the samples as high as 30% on fields of 15T. Ligas semicondutoras III-V nitreto diluídas possuem propriedades físicas que as tornam interessantes para aplicações em dispositivos optoeletrônicos. A possibilidade de casar liga de GaAsPN com silício faz com que esse semicondutor se torne interessante para estudos. Nesta dissertação investigamos as propriedades ópticas e magneto ópticas de nanoestruturas semicondutoras do tipo GaP(N)/GaAsPN. Foram realizadas medidas de fotoluminescência (PL), fotoluminescência de excitação (PLE) e magneto fotoluminescência (Magneto-PL) sob altos campos magnéticos (B ≤ 15T), em filmes finos de GaAsPN e múltiplos poços quânticos (MQW) de GaAsPN/GaPN. Estudamos efeitos de localização dos portadores através da análise do deslocamento diamagnético da PL, deslocamento Stoke e a dependência da posição do pico de fotoluminescência com a temperatura. Verificamos um deslocamento diamagnético negativo para algumas das amostras, o que é um comportamento anômalo nesse tipo de sistema. Foi verificado também um deslocamento para o vermelho do pico de PL quando realizado tratamento térmico nas amostras de MQWs. Analisando as propriedades de polarização de spin desse material, utilizando magneto-PL resolvida em polarização circular, foi observada uma polarização circular de até 30% num campo de 15 T.

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Bak, Junyung. "Photoluminescence and Raman Scattering Studies in Zn1-xCoxSe and GaAs:C Under Hydrostatic Pressure /." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487933245539353.

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Costa, Wangner Barbosa da [UNESP]. "Preparação e caracterização óptica de filmes nanocristalinos de GaAs:H depositados por RF magnetron sputtering." Universidade Estadual Paulista (UNESP), 2007. http://hdl.handle.net/11449/88484.

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Made available in DSpace on 2014-06-11T19:23:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-09-19Bitstream added on 2014-06-13T19:50:19Z : No. of bitstreams: 1 costa_wb_me_bauru.pdf: 1013500 bytes, checksum: af2a82e89ba237d24c1ff8441a9da739 (MD5) Secretaria de Educação do Estado de São Paulo Filmes nanocristalinos e amorfos de GaAs tem recentemente chamado a atenção de vários grupos de pesquisa devido as suas possíveis aplicações em novos dispositivos ópticos e eletrônicos. Igualmente atraentes são as novas propriedades físicas relacionadas com a estrutura nanocristalina e os efeitos da desordem na estrutura eletrônicas destes materiais. Entre as aplicações existentes, podemos citar o uso destes filmes como camadas anti-guia em lasers com emissão perpendicular à superfície, as camadas “buffer” em hetero-epitaxias de GaAs sobre Si, e os filtros interferométricos para a região do infravermelho. A preparação e a caracterização de filmes nanocristalinos de GaAs hidrogenados e não hidrogenados usando a técnica de RF magnetron sputtering foram focalizados neste trabalho. Um alvo de GaAs e uma atmosfera controlada contendo quantidades variáveis de argônio (Ar) e hidrogênio (H2) foram usadas na deposição do filme. Foi investigada a influência do fluxo de Ar e H2 na composição, estrutura e propriedades ópticas dos filmes. A influência da temperatura de substrato e potência de deposição também foi analisada. As técnicas de difração de raios-X e análise da energia de dispersão por emissão de raios-X (EDX), foram utilizadas na análise da estrutura e composição do filme, enquanto medidas ópticas de transmitância e refletância permitiram a determinação do coeficiente de absorção óptica e índice de refração dos filmes. A presença de ligações de hidrogênio nos filmes foi confirmada pelas bandas de absorção do Ga-H e As-H usando um espectrofotômetro de transformada de Fourier (FTIR). Os resultados mostram que a microestrutura, a composição e as propriedades ópticas do material são fortemente influenciadas por todos os parâmetros investigados, com destaque para o fluxo de hidrogênio utilizado nas deposições... The nanocrystalline and amorphous GaAs films are recently attracting the attention of several research groups due to their possible application in new electronic and optical devices. Also attractive are the new physical properties related to the nanocrystalline structure and the effects of disorder in the electronic structure of these materials. Among the existing applications we can mention the use of these films as antiguide layers in surface emitting lasers, as buffer layers in the GaAs hetero-epitaxy onto Si substrates, and as infrared interferometric filters. The preparation and characterization of hydrogenated and non-hydrogenated nanocrystalline GaAs films using the RF magnetron sputtering technique were focused here. An electronic grade GaAs water target and an atmosphere composed of variable amounts of Ar and 'H IND.2' were used in the film depositions. We have investigated the influence of Ar and 'H IND.2' fluxes on composition, structure, and optical properties of the films. The influence of substrate temperature and deposition power were also analyzed. X-ray diffraction and energy dispersive electron analysis (EDX) were used in the analysis of the film structure and composition, while optical transmittance and reflectance measurements allowed the determination of the optical absorption coefficient and refractive index of the films. The presence of bonded hydrogen in the films was confirmed by the Ga-H and As-H absorption bands using Fourier transform infrared spectra (FTIR). The results show that the microstructure, the composition, and the optical properties of the material are strongly influenced by all the investigated parameters, in special the hydrogen flux used in the depositions. The hydrogenated films ('H IND.2' flux of 3.0 sccm / Ar flux of 20.0 sccm) produced at relatively low power (30W) and substrate temperature (60ºC), have presented the widest... (Complete abstract click electronic access below)

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Costa, Wangner Barbosa da. "Preparação e caracterização óptica de filmes nanocristalinos de GaAs:H depositados por RF magnetron sputtering /." Bauru : [s.l.], 2007. http://hdl.handle.net/11449/88484.

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Orientador: José Humberto Dias da Silva Banca: Américo Tabata Banca: Johnny Vilcarromero Lopez O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp Resumo: Filmes nanocristalinos e amorfos de GaAs tem recentemente chamado a atenção de vários grupos de pesquisa devido as suas possíveis aplicações em novos dispositivos ópticos e eletrônicos. Igualmente atraentes são as novas propriedades físicas relacionadas com a estrutura nanocristalina e os efeitos da desordem na estrutura eletrônicas destes materiais. Entre as aplicações existentes, podemos citar o uso destes filmes como camadas anti-guia em lasers com emissão perpendicular à superfície, as camadas "buffer" em hetero-epitaxias de GaAs sobre Si, e os filtros interferométricos para a região do infravermelho. A preparação e a caracterização de filmes nanocristalinos de GaAs hidrogenados e não hidrogenados usando a técnica de RF magnetron sputtering foram focalizados neste trabalho. Um alvo de GaAs e uma atmosfera controlada contendo quantidades variáveis de argônio (Ar) e hidrogênio (H2) foram usadas na deposição do filme. Foi investigada a influência do fluxo de Ar e H2 na composição, estrutura e propriedades ópticas dos filmes. A influência da temperatura de substrato e potência de deposição também foi analisada. As técnicas de difração de raios-X e análise da energia de dispersão por emissão de raios-X (EDX), foram utilizadas na análise da estrutura e composição do filme, enquanto medidas ópticas de transmitância e refletância permitiram a determinação do coeficiente de absorção óptica e índice de refração dos filmes. A presença de ligações de hidrogênio nos filmes foi confirmada pelas bandas de absorção do Ga-H e As-H usando um espectrofotômetro de transformada de Fourier (FTIR). Os resultados mostram que a microestrutura, a composição e as propriedades ópticas do material são fortemente influenciadas por todos os parâmetros investigados, com destaque para o fluxo de hidrogênio utilizado nas deposições... (Resumo completo, clicar acesso eletrônico abaixo) Abstract: The nanocrystalline and amorphous GaAs films are recently attracting the attention of several research groups due to their possible application in new electronic and optical devices. Also attractive are the new physical properties related to the nanocrystalline structure and the effects of disorder in the electronic structure of these materials. Among the existing applications we can mention the use of these films as antiguide layers in surface emitting lasers, as buffer layers in the GaAs hetero-epitaxy onto Si substrates, and as infrared interferometric filters. The preparation and characterization of hydrogenated and non-hydrogenated nanocrystalline GaAs films using the RF magnetron sputtering technique were focused here. An electronic grade GaAs water target and an atmosphere composed of variable amounts of Ar and 'H IND.2' were used in the film depositions. We have investigated the influence of Ar and 'H IND.2' fluxes on composition, structure, and optical properties of the films. The influence of substrate temperature and deposition power were also analyzed. X-ray diffraction and energy dispersive electron analysis (EDX) were used in the analysis of the film structure and composition, while optical transmittance and reflectance measurements allowed the determination of the optical absorption coefficient and refractive index of the films. The presence of bonded hydrogen in the films was confirmed by the Ga-H and As-H absorption bands using Fourier transform infrared spectra (FTIR). The results show that the microstructure, the composition, and the optical properties of the material are strongly influenced by all the investigated parameters, in special the hydrogen flux used in the depositions. The hydrogenated films ('H IND.2' flux of 3.0 sccm / Ar flux of 20.0 sccm) produced at relatively low power (30W) and substrate temperature (60ºC), have presented the widest... (Complete abstract click electronic access below) Mestre

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Guimaraes, P. S. S. "Electrical and optical studies of nsup(+)nnsup(+)GaAs and GaAs/(AlGa)As structures and of GaAs:Cr/Si." Thesis, University of Nottingham, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371124.

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Sani, Suleiman Muhammad. "Photo-commutateur à large bande en technologies guide d'onde coplanaire et microruban réalisé sur GaAs:Cr+ et sur Si." Grenoble INPG, 1992. http://www.theses.fr/1992INPG0167.

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Le controle optique de circuits microondes permet d'envisager des nouvelles applications, par exemple pour les reseaux d'antennes a dephasage, la generation de signaux microondes tres courts et a large spectre, pour l'instrumentation et le traitement du signal. L'effet photoconducteur est un des phenomenes physiques qui permet ce controle. Dans notre etude, nous avons realise et caracterise deux photo-commutateurs a large bande en technologies guide d'onde coplanaire et microruban realises sur gaas: cr#+ et sur si. A partir d'une modelisation phenomenologique du dispositif, nous avons propose un schema equivalent qui nous a permis de simuler le fonctionnement du photocommutateur. Nous avons concu et realise des montures de test permettant les caracterisations des dispositifs sans et avec eclairement permanent. Un premier photocommutateur a large bande (0,5 ghz-10 ghz) en technologie microruban realise sur si a permis d'obtenir un rapport on/off de 10 db. Nous avons aussi realise des photocommutateurs en technologies guide d'onde coplanaire et microruban sur gaas: cr+ avec une bande passante de 4 ghz et un rapport on/off de 10 db. La comparaison entre les resultats experimentaux et theoriques a permis de mettre en evidence les problemes presentes par les fils d'interconnexions et les parametres importants du fonctionnement des photocommutateurs et nous avons propose des voies d'amelioration en optimisant ces parametres

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Gao, Kun. "Highly Mismatched GaAs(1-x)N(x) and Ge(1-x)Sn(x) Alloys Prepared by Ion Implantation and Ultrashort Annealing." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-158921.

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Doping allows us to modify semiconductor materials for desired properties such as conductivity, bandgap, and / or lattice parameter. A small portion replacement of the highly mismatched isoelectronic dopants with the host atoms of a semiconductor can result in drastic variation of its structural, optical, and / or electronic properties. Here, the term "mismatch" describes the properties of atom size, ionicity, and / or electronegativity. This thesis presents the fabrication of two kinds of highly mismatched semiconductor alloys, i.e., Ge(1-x)Sn(x) and GaAs(1-x)N(x). The structural and optical properties of the prepared Ge(1-x)Sn(x) and GaAs(1-x)N(x) have been investigated. The results suggest an efficient above-solubility doping induced by non-equilibrium methods of ion implantation and ultrashort annealing. Pulsed laser melting promotes the regrowth of monocrystalline Ge(1-x)Sn(x), whereas flash lamp annealing brings about the formation of high quality GaAs(1-x)N(x) with room temperature photoluminescence. The bandgap modification of Ge(1-x)Sn(x) and GaAs(1-x)N(x) has been verified by optical measurements of spectroscopic ellipsometry and photoluminescence, respectively. In addition, effective defect engineering in GaAs has been achieved by flash lamp annealing, by which a quasi-temperature-stable photoluminescence at 1.3 µm has been obtained Dotierung ermöglicht es, die Eigenschaften von Halbleitermaterialien, wie Leitfähigkeit, aber auch Bandabstand und / oder Gitterkonstanten gezielt zu verändern. Wenn ein Halbleiter mit einer kleinen Menge unterschiedliche Fremdatome dotiert wird, kann dies in einer drastischen Modifikation der strukturellen, optischen und / oder elektronischen Eigenschaften resultieren. Der Begriff "unterschiedlich" bedeutet hier die Eigenschaften von Atomgröße, Ioniztät und / oder Elektronegativität. Diese Doktorarbeit beschreibt die Herstellung von zwei Arten von stark fehlangepassten Halbleiterlegierungen: Ge(1-x)Sn(x) und GaAs(1-x)N(x). Die strukturellen und optischen Eigenschaften von Ge(1-x)Sn(x) und GaAs(1-x)N(x) wurden untersucht. Die Ergebnisse deuten auf eine effiziente Dotierung oberhalb der Löslichkeit, induziert durch die Nicht-Gleichgewichtsverfahren Ionenimplantation und Ultrakurzzeit-Ausheilung. Gepulstes Laserschmelzen ermöglicht das Nachwachsen von monokristallinem Ge(1-x)Sn(x), während die Blitzlampenausheilung in der Bildung von GaAs(1-x)N(x) hoher Qualität mit Photolumineszenz bei Raumtemperatur resultiert. Die Änderung der Bandlücke von Ge(1-x)Sn(x) und GaAs(1-x)N(x) wurde durch die optischen Methoden der spektroskopischen Ellipsometrie und Photolumineszenz verifiziert. Darüber hinaus konnte in ausgeheiltem GaAs eine quasi-temperaturstabile Photolumineszenz bei 1,3 µm beobachtet werden

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Brilhault, Annick. "CONTRIBUTION A L'ETUDE DE CERTAINS ELEMENTS DE TRANSITION DANS LES SEMICONDUCTEURS PAR METHODE DE PHOTOCONDUCTIVITE (GaAs:V, Si:Au, Si:Pt)." Toulouse, INSA, 1987. http://www.theses.fr/1987ISAT0027.

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ETUDE DE TROIS ELEMENTS DE TRANSITION DANS LES SEMICONDUCTEURS PAR PHOTOCONDUCTIVITE. 1)GaAs: NOUS PROPOSONS UN NIVEAU SCHEMA D'ENERGIE. UN NIVEAU SIMPLE ACCEPTEUR (V)**(O)/(V)**(-) A E::(C)-0,16 EV ET UN NIVEAU DOUBLE ACCEPTEUR (V)-/(V), A Ec- 0,65 eV. 2)Si:Au NOUS CONFIRMONS LES POSITIONS RESPECTIVES DES NIVEAUX DONNEUR ET ACCEPTEUR LIES A L'OR A Ev + 0,35 eV ET Ev + 0,63 eV. 3)Si:Pt LES EXPERIENCES REALISEES ONT MIS EN EVIDENCE LE NIVEAU ACCEPTEUR (o/-) DU PLATINE SUBSTITUTIONNEL A UNE ENERGIE DE 0,915 eV PAR RAPPORT A LA BANDE DE VALENCE

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Eßer, Faina. "Cyclotron resonance and photoluminescence studies of dilute GaAsN in magnetic fields up to 62 Tesla." Helmholtz-Zentrum Dresden-Rossendorf, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-210245.

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In this thesis, we investigate optical and electrical properties of dilute nitride semiconductors GaAsN in pulsed magnetic fields up to 62 T. For the most part, the experiments are performed at the Dresden High Magnetic Field Laboratory (HLD). In the first part of this thesis, the electron effective mass of GaAsN is determined with a direct method for the first time. Cyclotron resonance (CR) absorption spectroscopy is performed in Si-doped GaAsN epilayers with a nitrogen content up to 0.2%. For the CR absorption study, we use the combination of the free-electron laser FELBE and pulsed magnetic fields at the HLD, both located at the Helmholtz-Zentrum Dresden-Rossendorf. A slight increase of the CR electron effective mass with N content is obtained. This result is in excellent agreement with calculations based on the band anticrossing model and the empirical tight-binding method. We also find an increase of the band nonparabolicity with increasing N concentration in agreement with our calculations of the energy dependent momentum effective mass. In the second part of this thesis, the photoluminescence (PL) characteristics of intrinsic GaAsN and n-doped GaAsN:Si is studied. The PL of intrinsic and very dilute GaAsN is characterized by both GaAs-related transitions and N-induced features. These distinct peaks merge into a broad spectral band of localized excitons (LEs) when the N content is increased. This so-called LE-band exhibits a partially delocalized character because of overlapping exciton wave functions and an efficient interexcitonic population transfer. Merged spectra dominate the PL of all Si-doped GaAsN samples. They have contributions of free and localized excitons and are consequently blue-shifted with respect to LE-bands of intrinsic GaAsN. The highly merged PL profiles of GaAsN:Si are studied systematically for the first time with temperature-dependent time-resolved PL. The PL decay is predominantly monoexponential and has a strong energy dispersion. In comparison to formerly reported values of intrinsic GaAsN epilayers, the determined decay times of GaAsN:Si are reduced by a factor of 10 because of enhanced Shockley-Read-Hall and possibly Auger recombinations. In the third part of this thesis, intrinsic and Si-doped GaAsN are investigated with magneto-PL in fields up to 62 T. A magneto-PL setup for pulsed magnetic fields of the HLD was built for this purpose. The blue-shift of LE-bands is studied in high magnetic fields in order to investigate its delocalized character. The blue-shift is diminished in intrinsic GaAsN at higher temperatures, which indicates that the interexcitonic population transfer is only active below a critical temperature 20 K < T < 50 K. A similar increase of the temperature has no significant impact on the partially delocalized character of the merged spectral band of GaAsN:Si. We conclude that the interexcitonic transfer of Si-doped GaAsN is more complex than in undoped GaAsN. In order to determine reduced masses of undoped GaAsN and GaAs:Si, the field-induced shift of the free exciton transition is studied in the high-field limit. We find an excellent agreement of GaAs:Si with a formerly published value of intrinsic GaAs which was determined with the same method. In both cases, the reduced mass values are enhanced by 20% in comparison to the accepted reduced mass values of GaAs. The determined GaAsN masses are 1.5 times larger than in GaAs:Si and match the rising trend of formerly reported electron effective masses of GaAsN.

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Reis, Roberto Moreno Souza dos. "Estudo de camadas superficiais de SiC e GaAsN sintetizadas por implantação iônica em Si e GaAs." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2013. http://hdl.handle.net/10183/79514.

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Semicondutores de gap de banda grande possuem um vasto campo de aplicação na construção de dispositivos que necessitam operar em alta potência, em alta frequência e em ambientes hostis. Nesse trabalho apresentamos um estudo das sínteses de SiC e GaAsN obtidos, respectivamente, por implantação iônica de C em Si pré-implantado com He, e de N em substratos de GaAs. Uma camada de 110 nm de SiO2 foi depositada nos substratos antes do processo de implantação. Essa foi removida após a síntese, expondo as camadas à superfície. Para a síntese de SiC, substratos de Si préimplantados com He foram preparados a fim de gerar um estágio intermediário de substrato do ponto de vista de tensão exercida por esse na camada de SiC em síntese. Apresentamos diferenças entre a síntese do presente trabalho com as sínteses dos trabalhos anteriores, nos quais foram feitas a partir de Si bulk (tensão máxima) e a partir de SIMOX (sem tensão). Análises composicionais e estruturais foram feitas por Espectrometria de Retroespalhamento de Rutherford (RBS), Canalizacão (RBS/C) e Microscopia Eletrônica de Transmissão (TEM). Substratos pré-implantados com He nos levaram a uma redução na fluência mínima de C necessária para a síntese de uma camada de SiC estequiométrica, em comparação com o mesmo processo de síntese de SiC em SiO2/Si utilizando substratos de Si bulk. A fluência é comparável àquela necessária na síntese a partir de estruturas SIMOX, porém, a presente síntese apresentou uma importante melhora na qualidade estrutural. Na síntese de GaAsN por implantação de N em SiO2/GaAs, diferentes temperaturas de implantação foram utilizadas, partindo de temperatura ambiente até 500oC. Tratamentos térmicos em 850oC por 5 min foram feitos e diferenças estruturais foram extensamente estudadas por RBS, Fotoluminescência e TEM. Análise estrutural feita por TEM indica que a temperatura de implantação de 400oC é a mais adequada para a síntese de GaN cristalino. Temperaturas mais baixas que essa aumentam a tendência de formação de ligas GaAsN, no quais, para implantação em temperatura ambiente são amorfas. Condutividade tipo-p foi medida em ligas GaAsN:Mg obtidas por epitaxia de feixe molecular (MBE) e em amostras dopadas com Mg por implantação iônica em GaAsN amorfo obtido por MBE. Também exploramos a possibilidade de obtenção dessas ligas por co-implantação de N e Mg em substratos GaAs em temperatura ambiente. Semiconductors with a large band gap have a wide application in the construction of devices that need to operate at high power, at high frequency and in hostile environments. In this work we present studies about the synthesis of SiC and GaAsN obtained by ion implantation of C into Si pre-implanted with He, and N into GaAs substrates, respectively. About 110 nm of SiO2 layer was deposited on all substrates previously to the implantation procedures. This layer was removed after synthesis revealing the synthesized layers to the surface. For the SiC synthesis, Si substrates pre-implanted with He were prepared in order to generate an intermediate stress stage as applied by the substrate on the epitaxial SiC in synthesis. We present differences between the current synthesis and those performed in in previous works, where synthesis started from Si bulk (maximum stress) and from SIMOX structures (no stress). Compositional and structural analyses were undergone by Rutherford Backscattering Spectrometry (RBS), Channeling (RBS/C) and Transmission Electron Microscopy (TEM). Si substrates pre-implanted with He led us to a reduction in the minimum C fluence required for synthesis of a stoichiometric SiC layer, compared to the same SiC synthesis process in SiO2/Si using Si bulk substrates. Such fluence is comparable to the one required for the synthesis started from SIMOX structures, but the present synthesis now demonstrates an important structural quality improvement. For the GaAsN synthesis by N ion implantation into SiO2/GaAs, the samples were kept at different implantation temperatures, starting from room temperature (RT) up to 500oC. Thermal treatments at 850oC during 5 min were performed and structural differences were extensively studied by RBS, Photoluminescence and TEM measurements. Structural analysis performed by TEM indicates that the implantation temperature of 400oC is more adequate for the synthesis of a crystalline GaN layer. Lower temperatures enhance the tendency to form GaAsN alloys, which is particularly amorphous for the RT implantation case. In addition, p-doping of GaAsN using Mg was also addressed. P-type conductivity was measured in GaAsN:Mg alloys obtained by Molecular Beam Epitaxy (MBE) and in samples doped by Mg implantation into amorphous GaAsN grown by MBE. We also probed the possibility to obtain such allows by N and Mg co-implantation into GaAs substrates at room temperature.

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Almosni, Samy. "Growth, structural and electro-optical properties of GaP/Si and GaAsPN/ GaP single junctions for lattice-matched tandem solar cells on silicon." Thesis, Rennes, INSA, 2015. http://www.theses.fr/2015ISAR0010/document.

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Cette thèse se concentre sur la fabrication de cellule solaire IIIN- V sur substrat de GaP (001) et sur la croissance de couche de GaP sur Si (001). Le but est de réaliser des cellules solaires hautes efficacité sur un substrat à faible coût afin de les intégrer dans des centrales solaire photovoltaïque sous concentration. Les principaux résultats obtenus montrent : - L’importance de l’utilisation d’AlGaP en tant que couche de prénucléation pour annihiler les parois d’antiphase à l’interface GaP/ Si (néfaste pour les propriétés optoélectroniques des dispositifs) - De nombreuses similitude entre la croissance de GaAsN et de GaPN ce qui permet d’élaborer une stratégie afin d’optimiser les propriétés optoélectroniques du GaAsPN - De fortes corrélations entre les propriétés optique et éléctriques dans les nitrures dilués - La réalisation préliminaire d’une cellule solaire monojonction sur GaP ayant un rendement encourageant de 2.25% considérant la faible épaisseur de l’absorbeur dans cette cellule (300 nm) This thesis focuses on optimizing the heterogeneous growth of IIIN- V solar cells on GaP (001) and GaP nanolayers on Si (001). The goal is to build high efficiency solar cells on low-cost substrate for the realization of concentrated photovoltaic powerplant. The main results shows: - AlGaP as prenucleation layer increase the annihilations of anti-phase boundaries at the GaP/Si interface (harmful for the electronic properties of the devices). - Similarities between the growth of GaAsN and GaPN giving strategies to improve the GaAsPN electrical properties - Clear correlations between the optical and electrical properties of dilute nitride solar cells, giving interesting tools to optimize the growth of those materials using optical measurements. - The realization of a GaAsPN solar cell on GaP with a yield of 2.25%. This results is encouraging given the thin GaAsPN absorber used in this cell

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Azaizia, Sawsen. "Alliages à base de GaAs pour applications optoélectroniques et spintroniques." Thesis, Toulouse, INSA, 2018. http://www.theses.fr/2018ISAT0018/document.

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Ce travail de thèse est consacré à l’étude et au contrôle des propriétés de spin des électrons dans des structures à base de semi-conducteurs GaAs : GaAsN, GaAsBi et InGaAs. L'objectif est de donner une description fine de leurs propriétés électronique afin d'appréhender leur potentiel pour des applications en optoélectronique et spintronique. Nous avons focalisé l'étude des propriétés de spin des semi-conducteurs à base de nitrure dilué GaAsN sur les propriétés de l'interaction hyperfine entre l'électron et les noyaux des centres paramagnétiques naturellement présents dans ces matériaux. L'étude est réalisée par des expériences de photoluminescence pompe-sonde, en tirant parti du mécanisme de filtrage de spin par les centres paramagnétiques profonds présents dans le GaAsN massif : la recombinaison dépendante du spin (SDR). Nous démontrons, via l'enregistrement de la dynamique de la photoluminescence bande à bande, une nouvelle technique de détection des oscillations de spin cohérentes électron-noyau dues à l'interaction hyperfine. Ces oscillations sont observées dans l'application d'un champ magnétique externe et sans la nécessité d'utiliser les techniques de résonance de spin électronique. La caractérisation des matériaux bismures dilués GaAsBi en couches massives et en puits quantiques élaborés par épitaxie par jet moléculaire avec différentes concentrations de bismuth avec des expériences de spectroscopie de photoluminescence résolue en temps et en polarisation permet l’étude des propriétés de spin des électrons. Les résultats expérimentaux ont révélé une nette diminution du temps de relaxation de spin des électrons lorsque la fraction de bismuth augmente. Cette réduction significative du temps de relaxation de spin est liée à l'augmentation du couplage spin-orbite dans le matériau GaAsBi. La dynamique de relaxation observée est en bon accord avec le modèle de D'yakonov-Perel. Une troisième étude a porté sur le contrôle et la manipulation de spin des électrons dans les puits quantiques à semi-conducteurs III-V InGaAs/GaAs. Les hétérostructures élaborées sur des substrats d'orientation (111) présentent des propriétés de symétries particulières, qui combinées aux propriétés piézoélectriques, permettent sans application d’un champ électrique externe, de bloquer ou accélérer la dynamique de relaxation de spin. Ces observations démontrent la possibilité de contrôler le spin des porteurs à l'aide des propriétés intrinsèques de structures à puits quantiques, ce qui en fait de très bons candidats pour des applications futures de traitement et de stockage de l'information quantiques This thesis is devoted to the study of the electron spin properties for optoelectronic and spintronic applications of different GaAs-based semiconductor systems: GaAsN, GaAsBi, and InGaAs.The investigation of the spin properties of dilute nitride GaAsN-based semiconductors is centered on the properties of the hyperfine interaction between the electron and the nuclei at the paramagnetic centers naturally present in these compounds. The study is carried out, in the temporal domain, by a photoluminescence-based pump-probe technique and taking advantage of the spin-dependent relaxation mechanism via deep paramagnetic centers in GaAsN bulk. We demonstrate a novel detection scheme of the coherent electron-nuclear spin oscillations related to the hyperfine interaction and revealed by the band-to-band photoluminescence in zero external magnetic field and without the need of electron spin resonance techniques. GaAsBi semiconductors provide new opportunities for many optoelectronic applications thanks to possibility of greatly modulate the band gap and the spin-orbit interaction with the bismuth concentration. Using time-resolved photoluminescence spectroscopy experiment, we have characterized the optical and spin properties of bulk and quantum well GaAsBi structures elaborated by molecular beam epitaxy in a wide range of Bi-content. The experimental results revealed, on the one hand, the localization effect of exciton at low temperature and, on the other hand, the marked decrease of electron spin relaxation time when bismuth content increases. These results are consistent with Dyakonov-Perel spin relaxation mechanism whose efficiency is enhanced by the strong spin-orbit coupling interaction in GaAsBi alloy. The third study is focused on the demonstration of the control of the electron spin relaxation time in the III-V semiconductors by taking advantage of the symmetry properties allied to the piezoelectric effects in InGaAs (111)B heterostructures, without the need of any external electric field. We show that, in this system, the particular direction (111) associated with parameters related to InGaAs quantum wells such as indium concentration and quantum well width allows the control of spin electron relaxation time via piezoelectric field induced by the strain amplitude in the well. These observations demonstrate the possibility of monitoring electron spin relaxation process using intrinsic quantum confined structures, making them ideal candidates for use in quantum information storage and processing devices

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Auvray, Laurent. "EPVOM du matériau InGaAs-InP avec l'arsine ou le triméthylarsenic et du nitrure à petit gap GaAsN-GaAs : utilisation de l'azote comme gaz vecteur." Lyon 1, 2001. http://www.theses.fr/2001LYO19001.

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Les matériaux InGaAs et GaAsN ont été élaborés par EPVOM en utilisant comme gaz vecteur H2 ou N2. Un inconvénient de l'EPVOM est l'utilisation d'hydrures (arsine, phosphine) très toxiques, stockés sous haute pression. Par contre le triméthylarsenic (TMAs) est un composé peu toxique, liquide à température ambiante. Nous présentons une étude comparative entre le TMAs et l'arsine pour la croissance de In0,53Ga0,47As/InP, en association avec le triméthylindium et le triméthylgallium (TMG). La substitution du TMAs à l'arsine induit une dégradation des propriétés morphologiques (AFM), électriques et optiques des couches, tendance dramatiquement accentuée sous gaz vecteur N2. En revanche, avec l'arsine, des couches de qualité électronique équivalente sont obtenues avec H2 ou N2. Les nitrures Ga(In)AsN s'imposent aujourd'hui comme une voie pour réaliser l'émission à 1,3 micromètre sur substrat GaAs. Cette longueur d'onde, utile pour les Télécommunications optiques, est accessible car l'incorporation de faibles quantités d'azote réduit fortement le gap du matériau. Cependant, cette incorporation est difficile est nécessite des conditions de croissance fortement hors-équilibre. Nous avons privilégié le gaz vecteur N2 car il facilite cette incorporation. La 1,1-diméthylhydrazine a été choisie comme précurseur de l'azote, associée au TGM et à l'arsine. L'incorporation de l'azote a été étudiée en fonction des paramètres de croissance. Son influence sur le mode de croissance des couches a été explorée. Les propriétés optiques ont été caractérisées par photoluminescence (PL) et par photoréflectivité. L'incorporation d'azote dégrade fortement la luminescence du matériau. Cependant, un recuit post-croissance des couches, dans des conditions optimisées, permet une amélioration spectaculaire de leur qualité optique. L'émission de PL à basse température a pour origine la recombinaison d'excitons localisés. À plus haute température, elle est dominée par la recombinaison d'excitons libres.

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29

Sinning, Steffen. "Ultraschnelle optoelektronische und Materialeigenschaften von Stickstoff-haltigem GaAs." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1144482170985-90756.

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This work summarizes properties of nitrogen containing GaAs, which are relevant for optoelectronic application and allow a deeper insight in the physics of this material. In the first part the dependence of the banggap energy of nitrogen implanted GaAs on several process parameters (implanted nitrogen concentration, implantation temperature, annealing duration and temperature) is investigated. The second part focuses on the relaxation dynamics of highly excited carriers. For this, the carrier relaxation dynamics in nitrogen implanted GaAs, in epitaxially grown GaAsN and in (pure) GaAs are investigated by means of pump probe measurements on a femtosecond time scale. The comparision of experimental results to calculated scattering rates leads to relevant informations of scattering mechanisms and electronic properties Diese Arbeit widmet sich Eigenschaften von Stickstoff-haltigem Gallium-Arsenid, die sowohl für das physikalische Verständnis als auch für optoelektronische Anwendungen dieses Materials relevant sind. Im ersten Teil dieser Arbeit wird die Abhängigkeit der Bandlücken-Energie von verschiedenen Prozess-Parametern (Stickstoffkonzentration, Implantationstemperatur, Ausheildauer und -temperatur) in Stickstoff-implantiertem GaAs untersucht. Der zweite Teil konzentriert sich auf die Relaxationsdynamik hoch angeregter Ladungsträger. Neben dem oben bereits angesprochenen Material wird in Anrege-Abfrage-Experimenten mit Femtosekunden-Zeitauflösung zusätzlich epitaktisch gewachsenes GaAsN und (Stickstoff-freies) GaAs untersucht. Die Berechnung der Streuraten und der Vergleich mit experimentell gewonnenen Daten liefert wesentliche Informationen über beteiligte Steumechanismen und elektronische Eigenschaften

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Sinning, Steffen. "Ultraschnelle optoelektronische und Materialeigenschaften von Stickstoff-haltigem GaAs." Doctoral thesis, [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=979642523.

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Bourgard, João Baptista. "Nanofios de GaAs dopados com Si crescidos em substratos de GaAs e Si: análise estrutural e ótica." Master's thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/16258.

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Mestrado em Engenharia Física No presente trabalho foram estudadas três amostras contendo nanofios de GaAs crescidos por epitaxia de feixe molecular, com uma dopagem nominal de 1016 cm-3, sobre substratos de GaAs (100), GaAs(111)B e Si(100). Imagens obtidas por microscopia eletrónica de varrimento permitiram a identificação de direções de crescimento particulares em ambos os substratos de GaAs, e de um predomínio da direção vertical para o crescimento sobre GaAs(111)B. A presença da fase da wurtzite nos nanofios foi confirmada por medições de difração de raios-X e espectroscopia de Raman. Os parâmetros de rede desta estrutura cristalina foram estimados e estão em concordância com os resultados presentes na literatura. Por sua vez, as medições de fotoluminescência sugerem que todas as transições radiativas observadas tenham origem nos interfaces da heteroestrutura do tipo-II criada pela alternância, ao longo do eixo do nanofio, de segmentos de fases da blenda de zinco e da wurtzite. Foram também identificados dois mecanismos de desexcitação não radiativos sendo que um deles resulta do envolvimento de um nível discreto atribuído à presença de defeitos nos nanofios, enquanto o outro mecanismo de desexcitação, dominante para altas temperaturas, está relacionado com a libertação do portador de carga mais fracamente ligado, para a banda de energia respetiva. Verificou-se que os nanofios crescidos sobre o substrato de GaAs(111)B apresentam uma menor razão sinal/ruído atribuída a uma maior quantidade de defeitos não radiativos ou a uma menor densidade linear de interfaces entre ambas as fases cristalinas. Foi também observada um maior número de transições radiativas para os nanofios crescidos sobre o substrato de Si(100), o que pode estar relacionado com a existência de uma elevada dispersão de larguras dos segmentos. Este estudo ótico permitiu ainda identificar fortes semelhanças entre algumas das transições radiativas em amostras diferentes o que sugere que estas recombinações tenham origem em defeitos e/ou heteroestruras similares. In the present work, three samples containing GaAs nanowires grown by molecular beam epitaxy, with a nominal doping of 1016 cm-3, on GaAs (100), GaAs(111)B and Si(100) substrates, were studied. Scanning electron microscopy images allowed the identification of particular growth directions on both GaAs substrates and a predominant vertical alignment in the case of nanowires grown on the GaAs(111)B substrate. The presence of the wurtzite phase in the nanowires was confirmed by X-Ray diffraction and Raman spectroscopy measurements. The lattice parameters of this crystalline structure were estimated and are in good agreement with the reported results in the literature. The photoluminescence measurements suggest that all the observed radiative transitions originate a type-II heterostructure created by the zinc blend and wurtzite alternating segments along the nanowire axis. Two non-radiative de-excitation mechanisms were also identified, one resulting from the participation of a discrete level assigned to the presence of defects in the nanowire, while the other is related to the release of the least bound charge carrier to the respective band. A lower signal-to-noise ratio was observed for the nanowires grown on GaAs(111)B which might be related to a higher number of non radiative defects or a lower linear density of interfaces between the two crystalline phases. In addition, it was found that the number of observed radiative transitions is higher for the nanowires grown on Si(100) substrate, which can be related to a high dispersion of segment dimensions. This optical study also allowed the identification of strong similarities between some of the radiative transitions in different samples, which suggests that these radiative recombinations originate from defects and/or similar heterostructures.

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Elm, Matthias [Verfasser]. "Tuning the magnetic interactions in GaAs:Mn/MnAs hybrid structures by controlling shape and position of MnAs nanoclusters / vorgelegt von Matthias Thomas Elm." 2010. http://d-nb.info/1010566016/34.

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Titov, Andrey. "Propriétés électroniques des semiconducteurs magnétiques dilués: Ga_1-xMn_xN, Ga_1-xMn_xAs, Ge_1-xMn_x." Phd thesis, 2006. http://tel.archives-ouvertes.fr/tel-00113864.

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Les propriétés électroniques de (Ga,Mn)N ont été étudiées par spectroscopie d'absorption des rayons X au seuil K du Mn. Des calculs ab-initio ont été utilisés pour interpréter les spectres d'absorption de (Ga,Mn)N. Deux pré-pics sont présents dans le seuil du Mn: le premier pré-pic est attribué aux transitions électronique vers les états 3d du Mn de spin up, tandis que le second pré-pic correspond aux transitions vers les états 3d du Mn de spin down. Cette interprétation nous permet de déterminer que l'état électronique du Mn dans (Ga,Mn)N est Mn3+: deux pré-pics sont présents dans les spectres d'absorption du Mn3+ et un seul pré-pic reste dans les spectres du Mn2+. Ce changement des spectres a été vérifié expérimentalement sur des échantillons de (Zn,Mn2+)Te et (Ga,Mn2+)As. De plus, cette interprétation permet d'étudier la distribution du Mn dans (Ga,Mn)N: la forme des spectres d'absorption suggère que la distribution du Mn est homogène dans nos échantillons de (Ga,Mn)N.

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Keipper, Phillip J. "InP:Fe and GaAs:Ce picosecond photoconductive radiation detectors." Thesis, 1985. http://hdl.handle.net/10945/21385.

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Ma, Ta-Chun, and 馬大鈞. "Molecular Beam Epitaxy of GaAsSbN and Its Applications." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/59098703070784293731.

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博士 臺灣大學 電機工程學研究所 98 In this dissertation, we use a RF-plasma-assisted molecular beam epitaxy system to investigate the growth of GaAsSbN mixed-group V alloys. Our research topics include the characterization of plasma source, the incorporation behavior of the N in GaAsSbN, optical properties of lattice-matched GaAsSbN and the characteristic of GaAs/GaAsSbN heterojunctions on GaAs substrate. Due to the complexity of the plasma source, we use optical emission spectroscopy and quadruple mass spectroscopy to identify the relation between the operation parameters and N-radical species. We placed a shutter in front of the plasma aperture, and obtained atomic N-radical source for GaAsSbN growth. We found that N incorporation in GaAsSbN grown with atomic N-radicals decreases with the increase of Sb flux, which is very different from that of samples grown with meta-stable molecular N-radicals. Through the study of plasma characterization, we also found that the condition with low RF power, low N2 flow rate, and without the blocking of shutter can provide a source dominated by meta-stable molecules. When meta-stable molecule source is used, the N incorporation in GaAsSbN grown with meta-stable molecule source increases with the increase of Sb flux, which is consistent with the reports in literature. Based on the results of plasma characterization, we have successfully grown lattice-match GaAsSbN epilayers on GaAs substrates. The lowest absorption edge achieved in this study is as low as 0.8 eV. In addition, according to the results of PL measurement, we found that the samples grown at 420 oC have the strongest PL intensity resulting from better homogeneity, as compared with samples grown at other temperatures. Finally, we fabricated and characterized n+-GaAs/p-GaAsSbN/p+-GaAs heterojunctions. We found that when GaAsSbN exceeds a certain thickness, inhomogeneity related defects begin to be generated in the epilayer. After thermal annealing, the optimum GaAsSbN thickness is 500 nm and the conversion efficiency under AM1.5G solar simulator is 3.6%. The high forward-biased current of the heterojunctions results in low open-circuited voltage. After the junction passivation with SiN and SiO2, the open-circuited voltage increases by 50 % and the conversion efficiency increases by 60% to 5.7%.

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Wu, Jiansheng, and 吳健生. "Raman scattering study of material properties of GaAsSbN." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/38440392534260026429.

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Wu, Jiann Shi, and 吳建羲. "Optimized Epitaxial Growth of GaAs:Si Infrared Emitting Diodes." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/49795437269116827231.

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碩士 中原大學 應用物理學系 82 The epitaxial wafers of GaAs:Si infrared emitting diodes were grown by the horizentol multi-bin slide-boat liquid phase epitaxial system. The major objects in this experiments were to find the optimum condition of the epitaxial growth of GaAs:Si infrared emitting diodes . It consists of the x-vaule and the dopant of window layer, the etch pit density of substrate, the thickness of n-GaAs:Si layer, and p-GaAs:Si. When it achieves the optimum condition, its relative emission intensity is 3 times as high as the conventional GaAs:Si homostructure infrared emitting diodes. In window layer, it was doped with magmesium(Mg) instead of silicon(Si). Because the concentration of the window layer can easy achieve the higher value.

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Chuang, Ming-Hung, and 莊銘宏. "Electrical and optical studies of GaAsN bulk and GaAsN/GaAs single quantum well." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/15524715749377520280.

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碩士 國立交通大學 電子物理系 89 The electrical and optical characteristics of GaAsN bulk and GaAsN/GaAs single quantum wells (SQW) were investigated by varying the GaAsN thickness and Nitrogen composition. The samples were grown by low-pressure Metalorganic Chemical Vapor Deposition (MOCVD) on n+ GaAs (100) substrates. The Nitrogen composition and well thickness were determined from x-ray diffraction patterns. The compositions of nitrogen were 0.9﹪for bulk, 1.2﹪for 250Å SQW and 1.8﹪for 40, 60, 250, 295 and 590Å SQWS. Electrical characteristics were investigated by current-voltage, capacitance-voltage, admittance spectroscopy and deep level transient spectroscopy (DLTS). The GaAs0.991N0.009 bulk sample was shown to be highly resistive with an activation energy of 0.47eV determined from the admittance spectroscopy for its resistance. Two defect levels at 0.16 and 0.72eV were observed by DLTS. Carrier confinement was observed for SQW/GaAs0.982N0.018 samples with thickness of 40 and 60 Å. Carrier depletion was observed for SQW samples with well thickness from 250Å to 590Å. Three traps at 0.34, 0.45 and 0.75eV were found by DLTS and admittance spectroscopy for 250Å SQW/GaAs0.982N0.018. Among the three traps, the traps at 0.34 and 0.75eV were also observed in 250Å SQW/GaAs0.991N0.009 sample. The trap at 0.34eV was shown to be responsible for the carrier accumulation observed in high-frequency measurement and carrier depletion observed in low-frequency measurement around the well region. The trap at 0.75eV was speculated to be EL2 trap. Because of the good quality of the quantum structure shown by PL and x-ray diffraction patterns s, the traps at 0.34 and 0.45eV were speculated to be Nitrogen-related impurities or point defects. For 290 Å SQW GaAs0.982N0.018 sample, the trap at 0.49eV was found to be mainly responsible for the carrier depletion observed in the sample.

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Chen, Tsung-Yi, and 陳宗億. "Photoluminescence study of GaAsSbN bulk epilayers on GaAs substrates." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/42417902872741183295.

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碩士 臺灣大學 電子工程學研究所 95 The photoluminescence (PL) properties of dilute nitride GaAsSbN bulk epilayers are investigated. The GaAsSbN samples were grown on GaAs substrates by gas-source molecular beam epitaxy and characterized after a thermal annealing at 800℃ for 5 min. The main PL peak energy of all the samples shows “S-shape” behavior in the low temperature region, which is attributed to the behavior of the emission from band-tail states, and fits the empirical Varshni curve in the high temperature region, which evidences the band edge luminescence, in the temperature-dependent measurement. Samples grown at 490℃ are with more significant “S-shape” behavior than the ones grown at low temperature, indicating the worse compositional homogeneity in the former samples. Through a comparison between the room temperature PL energy and the GaAsSb energy gap reported in literatures, we found that the energy reduction due to nitrogen incorporation in GaAsSbN is independent of the Sb composition, implying that the energy positions of the conduction and valence band can be independently controlled by N and Sb composition respectively. We also found that the Varshni parameters of all the samples are close to those of GaAsN with similar N composition. Beside the main peak, a broad deep PL emission peaking at ~0.7eV was also observed in most of the samples. The Arrhenius activation energies of the PL intensity were investigated. The activation energy of the band-tail emission fits their dissociation temperature quite well. For band edge luminescence at high temperature, we use a configuration-coordinate model, which is considered to be related to the deep level emission, to explain its activation energy successfully. Among the epilayers grown coherently on the GaAs substrate, the lowest room temperature PL energy is 0.84 eV. This result suggests that GaAsSbN is a promising material for GaAs-based long wavelength optoelectronic devices and tandem solar cells.

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Chang, Jui-Lin, and 張瑞麟. "The Electrical and Optoelectronic Characterizations of GaAs:As+ and GaN Materials." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/25040073224461153114.

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碩士 大同大學 光電工程研究所 88 We respectively study the current-voltage characteristics of AuGeNi contacts made on rapid-thermal annealed arsenic-ion-implanted S.I. GaAs (GaAs:As+) and Au contact made on S.I. GaN by using the measurements of TLM and I-V analysis. The key parameters such as leakage current, contact resistance, sheet resistance, specific contact resistivity, barrier height, breakdown voltage, saturation current, and photocurrent responsivity are primarily reported. For the GaAs:As+ materials, the mechanism responsible for the large dark current in the as-implanted GaAs:As+ is attributed to the hopping conduction of trapped carriers among the dense deep-level defects. After annealing, the defect density gradually reduces and the perfection of crystal lattice recovers. This results in the evanescence of the hopping conduction and the increasing resistance for GaAs:As+. The contact resistances are estimated to be ranged from 7.8x104 to 8x109 W as the annealing time increases from 0 to 300 seconds, respectively. The sheet resistances are increased from 2.4x104 to 2x1010 W/¨, and the specific contact resistances are increased from 13.8 to 1.6x105 W-cm2 as the annealing time increases. In comparison, the characteristic of the GaAs:As+ annealed for 5 minutes has the lower dark current. The current saturation and overshoot phenomenons in the conductivity of the GaAs:As+ diode are found. After annealing, the photocurrent tends to shift to lower applied voltage. The continuous-wave responsivity of the GaAs:As+ is measured to be 50 mA/W at bias of 30 volts. For the S.I GaN materials, the minumum leakage current of the diode with a 15-mm gap is about 55pA at bias of 1 volt, which is dramatically increased to 4 nA as the bias increases up to 10 volts. After alloying, the leakage current of the same device at bias of 10 volts further reduces to < 1 nA. The evaluated contact resistance, sheet resistance, and the specific contact resistances of the S.I. GaN diode biased at <10 volts are about 1.5´1010 W, 2.5x109 W/o, and 4.5x105 W-cm2 respectively, and are found to slightly increases after alloying. We find that the electrical characteristic of nearly S.I. GaN is similar to S.I. GaAs.

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Lin, Guo-Lung, and 林國隆. "Photoreflectance Study of InN and GaAsSbN-Third-Generation Photovoltaic Materials." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/f24cbn.

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碩士 國立中興大學 電機工程學系所 101 GaAsSbN and InN is the third-generation of solar cells related materials, so we study the GaAsSbN and InN of relevant characteristics to help the development of solar cells. In the last decade, low-nitrogen-containing III-V compound semiconductors have been extensively studied. Nitrogen adding into the semiconductor materials will cause significant reduction of the energy gap, because of the nitrogen atomic level and conduction band energy level interact with each other. The band will split and reduce the energy gap and at the same time reduce the lattice constant. So it’s suitable application for long-wavelength optoelectronic components. Photoreflectance (PR) spectrum has non-contact and non-destructive characteristics and a wide range of operating temperatures. It also has advantage of reducing background effects. Therefore, we use PR spectra to research the semiconductor materials GaAsSbN and use the double band anticrossing model to fit the PR results of GaAsSbN. For InN, we were using PR spectra, photoluminescence spectra, Raman spectroscopy to study the samples.We found that InN at temperatures above 100K is similar to metal conductors, andPR signals can not be measured. At temperature below 100K, InN will transform into the semiconductor-like properties, and PR signal can be measured. This results from free electrons cooling down to the trap states at such low temperatures. Then we fit the PR results at 30K to obtain the spin-orbit splitting and crystal field splitting values.The spin-orbit splitting and crystal field splitting are the basic parameters of semiconductors. So far there is no experimental values of InN in literature, but this thesis has achieved this goal.

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Lin, Chia-Hung, and 林嘉洪. "Studies on the properties of GaAsSbN/GaAs p-i-n devices." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/16091153464659436432.

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碩士 臺灣大學 電子工程學研究所 98 We study the fabrication and the properties of GaAs/GaAs0.97Sb0.02N0.01 heterjunction diodes deposited on GaAs. The energy gap of the GaAs0.97Sb0.02N0.01 layer is 1.17 eV. We found that all the forward currents are higher than the expected p/n junction diffusion current and increases as the GaAs0.97Sb0.02N0.01 layer thickness increases. In addition, the current is proportional to the perimeter instead of the area of the junction, suggesting that it originates from the recombination on the junction surface. From the Arrhenius plot of the saturation current, we found that the activation energy of the as-grown sample is close to half the energy gap of GaAs0.97Sb0.02N0.01, suggesting that the current is a defect recombination current. After thermal annealing, the activation energy increases, indicating the suppression of the surface recombination current. Coating SiN and SiN/SiO2 passivation layers on the junction surface significantly reduces both the reverse and forward currents. The passivated GaAs/ GaAs0.97Sb0.02N0.01 heterjunction shows an optimum conversion efficiency of 6.6% under 42 times of AM1.5G illumination.

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Chen, Chi-Kuang. "Study on the properties of GaAsSbN and the applications to Optoelectronic devices." 2008. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2007200811211300.

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Chen, Chi-Kuang, and 陳紀光. "Study on the properties of GaAsSbN and the applications to Optoelectronic devices." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/96127189615274483761.

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碩士 國立臺灣大學 電子工程學研究所 96 We have studied the effect of thermal annealing on the properties of GaAsSbN and the fabrication of GaAsSbN PIN devices. Passivation of Si and Be dopants in as-grown GaAsSbN was observed when the composition of nitrogen exceeded 1.7%. Although thermal annealing can improve the photoluminescence intensity and decrease the leakage current of the PIN junction, it results in high hole concentrations, leading to the conduction-type conversion in un-doped and Si-doped GaAsSbN. This phenomenon is ascribed to the generation of acceptor-type defects during the annealing process. After a comparative study on the device structures, we found that the N-on-P hetero-junction device has the best immunity to the type conversion effect resulting from the annealing process. Then, the effect of annealing temperature and duration on the device performance was systematically investigated. We found that annealing at 650

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Lin, Yang-Tin, and 林衍廷. "Studies on the optical and structural properties of bulk GaAsSbN epilayers on GaAs." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/54694231733680513868.

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碩士 國立臺灣大學 電子工程學研究所 95 In this study, the optical and structural properties of dilute nitride GaAsSbN epilayers, coherently grown on GaAs substrates by gas-source molecular beam epitaxy, have been investigated. The lowest room temperature absorption edge among these GaAsSbN is 0.80 eV, indicative of the promising applications on GaAs-based long wavelength optoelectronics and tandem solar cells. Optical and structural properties of the samples before and after rapid thermal treatment were characterized by using absorption spectroscopy, Fourier transform infrared spectroscopy, photoluminescence, electron probe microanalysis and X-ray diffratometry. Blue shift in the energy gap of all the samples was not observed until the annealing temperature was higher than 750

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Wang, Bo-Wei, and 汪柏維. "Short-range structure of dilute nitride GaAsSbN studied by X-ray absorption spectroscopy." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/17046445451374646152.

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碩士 國立臺灣大學 光電工程學研究所 102 This study is about the changes of the short-range configuration of N atoms in dilute nitride GaAsSbN after thermal annealing. We use valence force field model to construct 1000 atoms supercells with different N-centered short-range structure. Then we used FEFF9 program to calculate their XANES(X-ray absorption near edge structure) spectra. The XANES of N K-edge experiment result is compared with the simulations from FEFF9 to realize the short-range structure of N atoms, and the Sb K-edge EXAFS(extended X-ray absorption fine structure) fitting results of average GaSb bond length are compared to the VFF calculation to confirm the results. After comparing the results of XANES and EXAFS, we find there exist NN1 pairs along [0 0 1] direction with four Sb atoms clustering in their commom second shell, called NN1+Sb4 model. After thermal annealing at 800℃, some part of the NN1 pairs dissociate into isolated N with two Sb atoms clustering in the second shell. After 850℃ annealing, however, the short-range structure of N atoms is the isolated N+Sb2 model.

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Lin, Yan-Ting, and 林衍廷. "Effects of thermal annealing on the energy gap and atomic structure of GaAsSbN." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/52252473145140963846.

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博士 國立臺灣大學 電子工程學研究所 100 In this dissertation, the effects of thermal annealing on the energy gap and atomic structure of GaAsSbN, grown by gas source molecular beam epitaxy, have been investigated. From the measurement of photoluminescence and optical absorption, significant blue-shifts in energy gap, resulting from annealing with a temperature higher than 750C, were observed. The energy gap of the annealed GaAsSbN follows the band anticrossing model (BAC) reported in literature. Furthermore, the energy gap reduction can be independently controlled by Sb and N compositions. On the ground of this finding, we proposed a double BAC model, in which we suggest that N and Sb compositions control the energy of conduction and valence band respectively. Besides, the origin of the blue shift induced by thermal annealing is investigated. We believe N pairs NN1 responsible for the low energy gap of the as-grown GaAsSbN. Thermal annealing dissociates the pair into isolated N atoms, resulting in the blue-shift in energy gap. From the Kramers-Kronig modulus of photoreflectance measurement, we resolve multi-peaks relevant to different N pairs and isolated N. When the annealing temperature increases, the peaks gradually merge to that of isolated N. To further support the proposed N pairs dissociation theory, we performed N K-edge X-ray absorption near-edge spectroscopy (XANES) using the beam line 20A of National Synchrotron Radiation Research Center to study the short range structure of GaAsSbN. We use valence force field model to generate supercells with 216 atoms containing different atomic structures, including isolated N, NN1 pair, N-HBC complex, and so on. FEFF9 code, purchased from University of Washington, was then used to simulate the XANES spectra of N-centered cluster of 381 atoms, developed from supercells with different atomic structures. By comparing the experimental results with the simulated XANES, we conclude that NN1 pair existed in the as grown GaAsSbN sample. After thermal annealing at 850 C for 5 min, NN pairs transform into isolated N-HBC complex.

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Ping, Wang-Shang, and 王尚平. "Effect of annealing on the optical and electrical properties of dilute nitride GaAsSbN." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/03328153673638321292.

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碩士 國立臺灣大學 電機工程學研究所 97 This study is about the changes of electronic and optical properties that occur when the dilute nitride GaAsSbN is annealed. In our work, the effect of annealing temperature and duration on the bulk material was systematically investigated, trying to find an optimal annealing condition. Though the thermal treatment annihilates non-radiative centers, restores as-grown defects and enhances photoluminescence (PL) intensities, it induces acceptor-type defects and increases the hole concentrations in the samples, leading to the conduction-type conversion in un-doped GaAsSbN. The formation energy of the defect, determined from Arrhenius plot, is within 2.7~3.8 eV, revealing that the defects could be Ga vacancies. The improvement in PL intensity accompanies with the blue-shift in emission energy. And the origins of this annealing-induced blue-shift in PL peak energy include the homogenization of nitrogen atoms, the reduction in tail states, and the filling effect due to the increment in carrier density. We also compared MBE annealed samples with RTA annealed and the result shows that MBE annealed set can achieve higher PL intensity and better photo responsivity. Finally, we found that annealing at 600°C with longer duration can achieve higher PL intensity and less blue shift than at higher temperatures with shorter duration. At last, we have successfully fabricated GaAsSbN detectors with a cut-off wavelength >1.6 μm.

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""Propriedades ópticas e elétricas de filmes epitaxiais de GaAs:Si crescidos na superfície (311)A"." Tese, Biblioteca Digital de Teses e Dissertações da USP, 2002. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-03122002-103444/.

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Madini, Nassima. "Étude théorique des propriétés structurales et électroniques de l'alliage GaAsN." Thèse, 2004. http://hdl.handle.net/1866/17345.

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