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1
Cristea, Peter. "Molekularstrahlepitaxie im Materialsystem Ga(N, Sb)." [S.l. : s.n.], 2002. http://www.freidok.uni-freiburg.de/volltexte/563.
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Gies, S., M. J. Weseloh, C. Fuchs, W. Stolz, J. Hader, J. V. Moloney, S. W. Koch, and W. Heimbrodt. "Band offset in (Ga, In)As/Ga(As, Sb) heterostructures." AMER INST PHYSICS, 2016. http://hdl.handle.net/10150/622465.
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A series of (Ga, In)As/GaAs/Ga(As, Sb) multi-quantum well heterostructures is analyzed using temperature-and power-dependent photoluminescence (PL) spectroscopy. Pronounced PL variations with sample temperature are observed and analyzed using microscopic many-body theory and band structure calculations based on the k.p method. This theory-experiment comparison reveals an unusual, temperature dependent variation of the band alignment between the (Ga, In) As and Ga(As, Sb) quantum wells. Published by AIP Publishing.
3
Graf, Nikolaus Johannes Hubertus. "Molekularstrahlepitaxie in den Mischsystemen Ga(Sb,Bi) und In(Sb,Bi)." [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:25-opus-57744.
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Garandet, Jean-Paul. "Etude des phénomènes de transport et des défauts cristallins dans des alliages Ga-Sb et Ga-In-Sb élaborés par la méthode Bridgman." Grenoble INPG, 1989. http://www.theses.fr/1989INPG0058.
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Löber, Thomas Henning [Verfasser]. "Ga(As)Sb-Quantenpunkte und -Quantenpunkt-Laser / Thomas Henning Löber." München : Verlag Dr. Hut, 2011. http://d-nb.info/1018982159/34.
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6
LE, CLANCHE MARIE-CLAUDE. "Diagrammes de phases ni-ga-sb et er-ga-sb : applications a la metallurgie du contact ni/gasb et a la croissance epitaxiale d'heterostructures ersb/gasb." Rennes 1, 1995. http://www.theses.fr/1995REN10087.
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Dans la technologie des semiconducteurs sc iii-v, la fabrication reproductible de contacts (metal/sc iii-v) fiables et de bonne qualite reste un probleme imparfaitement resolu. Un contact ideal constitue d'un film metallique thermodynamiquement stable en presence du sc, peut etre obtenu par interdiffusion en phase solide d'une couche mince de metal avec le substrat. La complexite des interdiffusions dans les contacts (m/sc iii-v) comparees a celles dans les contacts (m/si) a conduit les technologues a envisager parallelement d'autres voies, comme l'epitaxie par jets moleculaires (ejm) de composes metalliques sur les sc iii-v. Les diagrammes ternaires ni-ga-sb et er-ga-sb, determines respectivement a 600 et 800c, sont caracterises par diffraction x, meb et microsonde. Celui de ni-ga-sb montre l'existence d'un phase ternaire originale derivee de la structure type nias. Les chemins de diffusion dans le couple ni/gasb sont determines a 550c par analyses quantitatives. Ceux-ci, tres complexes, temoignent de morphologies de zones de reaction perturbees par rapport a une stratification ideale. Les interdiffusions en phase solide entre un film de nickel et le substrat gasb, apres traitements thermiques entre 360 et 450c, et les epitaxies de films minces monocristallins de ersb sur gasb ont ete caracterisees par diverses techniques (diffraction x, rbs, met, rheed). L'etape finale des interdiffusions dans le contact (ni/gasb), conduit au melange des binaires ni#2ga#3 et nisb. Aucune de ces phases n'est un candidat ideal pour la realisation de contacts contrairement au compose binaire ersb qui presente avec gasb tous les criteres d'epitaxie et de stabilite thermodynamique requis. En effet, la croissance d'heterostructures ersb/gasb, puis gasb/ersb/gasb d'une qualite quasi parfaite a ete realisee
7
Nagu, Manikanda Prabu [Verfasser], and Barbara [Akademischer Betreuer] Albert. "Synthesis and thermoelectric studies of Zintl phases in the systems of Ba-Al-Sb, Ba-Ga-Sb, and Ba-In-Sb / Manikanda Prabu Nagu. Betreuer: Barbara Albert." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2014. http://d-nb.info/1110980167/34.
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Coudray, Paul. "Contribution à la passivation des photodétecteurs Ga(Al)Sb : étude de la sulfuration." Montpellier 2, 1993. http://www.theses.fr/1993MON20174.
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Avec la miniaturisation des composants microelectroniques, la passivation est devenue une etape indispensable de la fabrication des dispositifs. Une etude bibliographique de la sulfuration de gaas, m'a permis de proposer un protocole de stabilisation de la surface de gasb base sur une sulfuration par voie humide. Des analyses de surface telles que les spectroscopies de photo-electrons ou d'electrons auger et la spectro-ellipsometrie apportent des informations significatives sur la qualite des surfaces traitees. Une etude comparative de contacts schottky realises apres differents traitements permet de correler l'amelioration des caracteristiques electriques des contacts schottky a la qualite des surfaces sulfurees. L'integration de la sulfuration dans la technologie de fabrication des photodetecteurs mesa a base de ga(al)sb a conduit a une nette diminution des courants de fuite generes en surface
9
Rajabi, Mina. "Process optimization of IR detectors based on In(Ga)Sb QDs in InAs matrix." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-108221.
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This diploma project has been focused on optimization of the D2B IR detector fabrication process using different mesa sidewall treatments and passivation methods. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscope (AFM) measurements have been carried out on samples treated by different wet etching methods, to analyze their surface chemical composition and roughness. The surface roughness has been improved by critic etching, annealing and NaClO sequential treatment steps. Then these results have been utilized to improve the process of the D2B IR detectors. The dark current of the fabricated detectors passivated with various techniques have been characterized by I-V measurements at low (77 K) and room temperatures. The dark current mechanisms owing to surface shunt or bulk leakage are investigated by dark current temperature dependence analysis. By photoresist passivation devices with least leakage current are achieved.
10
Degtyareva, Olga. "X-ray diffraction studies of complex high-pressure phases of Bi, Sb, As, and Ga." Thesis, University of Edinburgh, 2003. http://hdl.handle.net/1842/13609.
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The work presented in this thesis applies advanced high-resolution powder diffraction techniques in combination with novel single-crystal diffraction techniques, recently developed in the Edinburgh High-Pressure Group, to studies of complex HP phases of group-V elements and Ga. The HP phases Bi-III and Sb-II, a subject of many experimental studies in the past and present, are shown to have an incommensurate host-guest structure, similar to that found in alkaline-earth elements. The basic host-guest structure is shown to be modulated, and a single-crystal diffraction study on Bi-III has revealed the true from of the modulation between the host and guest components. From HP powder diffraction studies of Sb, a new incommensurate host-guest phase Sb-II* is discovered, and a novel incommensurate to incommensurate phase transition is observed. The HP phase As-III is solved from powder diffraction data as a modulated incommensurate host-guest structure, and is shown to be the same as Sb-II*. Four-dimensional formalism is applied to the crystallographic description of these incommensurate phases. The group-III element Ga is known to have a complex HP behaviour with metastable effects and several phase transitions. The structure of the HP phase Ga-II was long believed to be cubic with 12 atoms in the unit cell but is shown from single-crystal diffraction data to be orthorhombic with 104 atoms in the unit cell. A new HP phase is discovered to be stable in Ga above the Ga-II phase, and its structure is solved from powder diffraction techniques as rhombohedral with 6 atoms in the unit cell, which represents a new structure type of an element. A revised phase diagram of Ga is proposed.
11
El, Haouari Ahmed. "Insertion électrochimique d'ions mcl#4# (m(al, ga, fe, sb) dans le graphite en milieu nitrométhane." Nancy 1, 1991. http://www.theses.fr/1991NAN10057.
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Ce travail est une contribution à l'étude des composes d'insertion obtenus par oxydation anodique du graphite en milieu nitrométhane. Il étend les études antérieures sur l'insertion d'anions fluorés mf#4# et mf#6#. Nous avons ainsi réalise la synthèse électrochimique de composés d'insertion inédits de formule générale c#a#n#+mcl#4# (ch#3no#2)#b avec m=al, ga, fe, sb. Les différents stades n ont été caractérisés par diffraction des rayons X (étude des réfections 001) et par analyses élémentaire et gravimétrique. Les études électrochimiques (voltamperometrie cyclique et potentiomètrie intensiostatique) ont permis de préciser les potentiels de formation des différents stades. Il apparait de façon générale que les stades i n'ont jamais pu être obtenus à l'exception du complexe graphite-sbcl#4#-ch#3no#2. Les stades ii, (m=al, ga, fe), jamais isolés à l'état pur, coexistent toujours à faible concentration avec les composes de stade III. Ceci est vraisemblablement lié à l'instabilité chimique des ions mcl#4# contenus dans l'électrolyte. Cette instabilité liée à la décomposition de mcl#4# contenus dans l'électrolyte. Cette instabilité liée à la décomposition de mcl#4# se traduit par la formation de chlore qui se dissout dans le nitrométhane. Cette réaction de décomposition semble se produire à un potentiel légèrement moins oxydant en présence de graphite. Par ailleurs, les ions mcl#4# sont stabilises à l'état inséré puisque leur décomposition entre les feuillets du graphite qui se caractériserait par l'exfoliation de ce dernier, n'a jamais été observée. L'insertion de incl#4# et de tlcl#4# n'a pu être mise en évidence alors qu'elle est possible dans les matériaux comme le polyacétylène. Il faut enfin signaler que les composes étudiés dans ce travail différent fondamentalement des composés parents obtenus par réaction directe d'halogénures mcl#3 sur le graphite même en présence de chlore comme l'indiquent les valeurs différentes des distances interplanaires: le rôle du solvant déjà signalé précédemment semble important
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Mohammad, Rezek Mahmoud Salim. "The Electronic Band Structure Of Iii (in, Al, Ga)-v (n, As, Sb) Compounds And Ternary Alloys." Phd thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606292/index.pdf.
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In this work, the electronic band structure of III (In, Al, Ga) - V (N, As, Sb)
compounds and their ternary alloys have been investigated by density functional
theory (DFT) within generalized gradient approximation (GGA) and empirical
tight binding (ETB) calculations, respectively.
The present DFT-GGA calculations have shown direct band gap structures
in zinc-blende phase for InN, InAs, InSb, GaN, and GaAs. However, indirect
band gap structures have been obtained for cubic AlN, AlSb and AlAs com-
poundshere, the conduction band minima of both AlN and AlAs are located at X symmetry point, while that of AlSb is at a position lying along Gamma- X direction. An important part of this work consists of ETB calculations which have been parameterized for sp3d2 basis and nearest neighbor interactions to study the band gap bowing of III(In
Al)- V(N
As
Sb) ternary alloys. This ETB model provides a satisfactory electronic properties of alloys within reasonable calculation time compared to the calculations of DFT. Since the present ETB energy parameters reproduce successfully the band structures of the compounds at ¡
and X symme- try points, they are considered reliable for the band gap bowing calculations of the ternary alloys. In the present work, the band gap engineering of InNxAs1¡
x, InNxSb1¡
x, InAsxSb1¡
x, Al1¡
xInxN, Al1¡
xInxSb and Al1¡
xInxAs alloys has been studied for total range of constituents (0 <
x <
1). The downward band gap bowing seems the largest in InNxAs1¡
x alloys among the alloys considered in this work. A metallic character of InNxAs1¡
x, InNxSb1¡
x and InAsxSb1¡
x has been ob- tained in the present calculations for certain concentration range of constituents (N
As) as predicted in the literature. Even for a small amount of contents (x), a decrease of the electronic e®
ective mass around ¡
symmetry point appears for InNxAs1-x, InNxSb1-x and InAsxSb1-x alloys manifesting itself by an increase of the band curvature. The calculated cross over from indirect to direct band gap of ternary Al alloys has been found to be consistent with the measurements. As a last summary, the determinations of the band gaps of alloys as a function of contents, the concentration range of con- stituents leading to metallic character of the alloys, the change of the electronic effective mass around the Brillioun zone center (Gamma) as a function of alloy contents, the cross over from indirect to direct band gap of the alloys which are direct on one end, indirect on the other end, are main achievements in this work, indispensable for the development of mate- rials leading to new modern circuit components.
13
Straßner, Johannes Helmut [Verfasser]. "Epitaktisches Wachstum und optoelektronische Eigenschaften von Ga(As)Sb-Quantenpunkten auf (Al)GaAs bei Variation der Barrieren / Johannes Helmut Straßner." München : Verlag Dr. Hut, 2016. http://d-nb.info/1106592735/34.
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Straßner, Johannes [Verfasser]. "Epitaktisches Wachstum und optoelektronische Eigenschaften von Ga(As)Sb-Quantenpunkten auf (Al)GaAs bei Variation der Barrieren / Johannes Helmut Straßner." München : Verlag Dr. Hut, 2016. http://d-nb.info/1106592735/34.
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Karouta, Fouad. "Thermodynamique des alliages Ga-in-As-Sb et application à la réalisation des structures émettrices de lumière à base de GaSb." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb375986866.
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Sterzer, Eduard [Verfasser], and Kerstin [Akademischer Betreuer] Volz. "(Ga,In)(N,As,Sb) Solar Cells: N Incorporation using Novel Precursor in MOVPE Growth and Solar Cell Characteristics / Eduard Sterzer ; Betreuer: Kerstin Volz." Marburg : Philipps-Universität Marburg, 2018. http://d-nb.info/116838012X/34.
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El, Bakkali Taheri Mohammed. "Automatisation de la mesure des propriétés de transport électronique d'alliages métalliques liquides étude des alliages or-polyvalents (Au Ga, Au Ge, Au In, Au Sb) /." Metz : Université Metz, 2008. ftp://ftp.scd.univ-metz.fr/pub/Theses/1994/El_Bakkali_Taheri.Mohammed.SMZ9460.pdf.
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El, Bakkali Taheri Mohammed. "Automatisation de la mesure des propriétés de transport électronique d'alliages métalliques liquides : étude des alliages or-polyvalents (Au-Ga, Au-Ge, Au-In, Au-Sb)." Metz, 1994. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1994/El_Bakkali_Taheri.Mohammed.SMZ9460.pdf.
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L'objectif de ce travail porte sur l'étude des propriétés de transport électronique d'alliages métalliques or-polyvalents dont la susceptibilité magnétique montre un minimum dans la zone de concentration riche en or. Ainsi nous avons mesuré, pour le première fois dans la plupart des cas, la résistivité électrique des alliages suivants : Au-Ga, Au-Ge, Au-In, Au-Sb. La précision des mesures a été améliorée sur un large domaine de température grâce à une gestion automatique du dispositif par un logiciel d'acquisition et de traitement de données mis au point à cet effet. La théorie des pseudopotentiel reste incapable d'expliquer nos mesures. Nous interprétons nos résultats à l'aide de la matrice t obtenue dans le cadre de la théorie de diffusion et exprimée en terme de déphasages dans le cadre de la théorie de Faber-Ziman. Nous avons discuté le choix de l'énergie de Fermi pour les deux types d'échange (Slater et Kohn-Sham) et nous avons procédé à une correction de celle-ci par ajustement sur la résistivité des corps purs. Une amélioration des résultats théoriques est envisageables par de nouvelles investigations au niveau du calcul des déphasages et de la détermination de l'énergie de FermiThe aim of this thesis is to study the transport properties of liquid noble métal-polyvalent alloys inwich the magnetic susceptibility shows a minimum in the gold rich side virsus the concentration. We have measured the electrical resistivity evolution as a function of the position of the polyvalent metal in the periodic table. The resistivity has been calculated using the phases shifts n (EF). Our calculation is based on two possible exchange tratement (Slater and Kohn-sham). We improved our results in taking into acount the energy dependence of phase shifts and using the Fermi energy obtained by a fit on the experimentals resisitivities of pure metals. A progress in theorical results are possible with some investigations in the phase shifts calculations and the Fermi energy determination
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Simons, Bethany Jane. "Processes controlling critical metal (Li, Be, Ga, Ge, Nb, Ta, In, Sn, Sb, W and Bi) distribution in the peraluminous granites of the Cornubian Batholith." Thesis, University of Exeter, 2015. http://hdl.handle.net/10871/17997.
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Critical metals are of growing economic importance for the low carbon sector but are susceptible to resource restrictions and have no viable substitutes in their applications. In this study, 134 samples of the Cornubian Batholith, SW England, with associated early Permian mafic and ultramafic rocks were sampled and analysed by ICP-MS and XRF for their major, trace and critical metal (Li, Be, Ga, Ge, Nb, Ta, In, Sb, W and Bi) abundance. The mineral chemistry of feldspars, micas, tourmaline, topaz and cordierite was determined for 8 samples by EPMA and LA-ICP-MS. The Cornubian Batholith is a peraluminous, composite pluton intruded into Devonian and Carboniferous metasedimentary and volcanic rocks. Geochemical fractionation trends recorded by whole rock geochemistry and mineral chemistry permit trace element modelling of two distinct fractional crystallisation series, biotite-muscovite (>282 Ma) and biotite-tourmaline (<282 Ma). The biotite-muscovite granites formed through muscovite and minor biotite dehydration melting of a metagreywacke source at moderate temperatures and pressures. Fractionation of an assemblage dominated by feldspars and biotite, enriched muscovite granites in Li (average 340 ppm), Be (13 ppm), Nb (16 ppm), Ta (3.7 ppm), In (77 ppb), Sn (17 ppm), W (12 ppm) and Bi (2.6 ppm) and are spatially associated with greisen style Sn-W mineralisation. Muscovite is the major host of In, Sn and W, and as muscovite is late-stage / subsolidus this implies these metals are highly incompatible in magmatic minerals and likely to partition into fluids exsolving from evolved muscovite granites. The biotite-tourmaline granites formed through higher-T melting than the first suite due to underplating of the region by mantle-derived melts during tectonic extension. Fractionation of feldspars, biotite and cordierite enriched Li (average 525 ppm), Ga (28 ppm), In (122 ppb), Sn (14 ppm), Nb (30 ppm), Ta (5.5 ppm), W (7.1 ppm) and Bi (2.7 ppm) in the tourmaline granites with retention of Be in the biotite granite due to partitioning of Be into cordierite. Distribution of Nb and Ta is controlled by accessory phases such as columbite within the evolved tourmaline granites, promoting disseminated Nb and Ta mineralisation. Lithium, In, Sn and W are hosted in biotite group micas which may prove favourable for breakdown on ingress of hydrothermal fluids and partitioning of the critical metals into mineralising fluids emanating from evolved tourmaline granites. Topaz granites are analogues of Rare Metal Granite described in France and Germany. They contain albite, polylithionite and topaz as major minerals and show differing trends on major and trace element plots relative to the other two granite series. These granites are enriched in Li (average 1363 ppm), Ga (38 ppm), Sn (21 ppm), W (24 ppm), Nb (52 ppm) and Ta (15 ppm) and formed through partial melting of a biotite-rich residue left after melting that formed early biotite granites.
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Nogaret, Alain. "Etude comparée du transport par effet tunnel résonnant dans les hétérostructures semiconductrices de type I et II en présence de pression hydrostatique et de fort champ magnétique." Toulouse, INSA, 1993. http://www.theses.fr/1993ISAT0037.
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Nous etudions la combinaison de l'effet tunnel resonnant avec l'effet tunnel interbande dans les heterostructures presentant un alignement de type ii. Dans les heterostructures de type i, la quantification magnetique montre qu'un electron avec une importante energie cinetique transverse conserve son energie plutot que son vecteur d'onde transverse, la pression hydrostatique met en evidence un pic de courant extraordinaire que nous attribuons a la formation de niveaux x lies dans les barrieres alas, le calcul clarifie la contribution des modes de phonons lo locaux au courant vallee. Nous exposons les procedes lithographiques que nous avons mis au point pour elaborer le systeme inas/alsb/gasb. Nous soulignons l'importance du choix de l'energie de fermi dans les electrodes et ses multiples consequences sur la forme des caracteristiques courant-tension des heterostructures de type ii. Nos resultats devoilent les mecanismes physiques responsables du courant resonnant interbande et suggerent l'existence d'une bande interdite d'hybridation due au couplage electron-trou. Nous interpretons l'effet tunnel interbande a travers des sous-bandes de trous par les regles de selection usuelles et observons pour la premiere fois la bistabilite intrinseque dans une structure de type ii. Ces resultats nous amenent a comparer les performances de dispositifs electroniques utilisant soit l'effet tunnel resonnant soit l'effet tunnel resonnant interbande
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Ichas, Valerie. "Étude sous pression des propriétés électroniques et magnétiques de composés de neptunium : NpGa3 et les monopnictures de Np : Net réalisation d'un réfrigérateur d'3He pour la mesure de la résistance électrique en dessous de 1,5K." Université Joseph Fourier (Grenoble ; 1971-2015), 1997. http://www.theses.fr/1997GRE10041.
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La resistance electrique des monopnictures de neptunium npas, npsb, npbi (structure nacl) et de npga#3 (structure aucu#3) a ete mesuree sous haute pression jusqu'a 25gpa et a basse temperature jusqu'a 1. 5k. Dans les monopnictures de np, la mise en ordre antiferromagnetique triple k (3k) produit une forte augmentation de la resistivite a pression ambiante. De plus, dans npsb et npbi, la resistivite montre un comportement semi-conducteur a basse temperature. Sous pression et dans les trois composes, la temperature d'ordre t#o#r#d diminue et la resistance chute discontinuement a basse temperature. La signature de l'ordre 3k est supprimee dans npas et npsb. L'anomalie kondo de la resistance disparait sous pression. La chute de resistance sous pression est interpretee par une modification de la surface de fermi qui coincide probablement avec la suppression de la phase 3k. Nous suggerons que la diminution de t#o#r#d est due a un changement de la surface de fermi en plus d'une legere delocalisation des electrons 5f. Dans npga#3, t#o#r#d augmente de 65k a 1bar jusqu'a 194k a 25gpa. L'anomalie kondo en resistivite est supprimee au dessus de 4gpa. Nos resultats suggerent que deux phases magnetiques sont presentes sous pression. Le comportement sous pression du moment ordonne et de la temperature d'ordre indique une faible delocalisation des electrons 5f. L'augmentation de la temperature d'ordre est expliquee par le renforcement des interactions d'echange indirectes entre ions magnetiques. Parallelement, nous avons developpe un prototype d'un refrigerateur #3he avec pompe a absorbtion par des charbons actifs. Il est destine a mesurer la resistance electrique de composes d'actinides en dessous de 1. 5k et sous haute pression. Le prototype permet d'atteindre des temperatures minimales de 650mk dans les conditions de mesures sous pression et 330mk dans les conditions de mesures a 1bar. Nous avons mesure avec succes la resistance electrique de np#4ru#7ge#6 jusqu'a 350mk et a pression ambiante
22
Nagu, Manikanda Prabu. "Synthesis and thermoelectric studies of Zintl phases in the systems of Ba-Al-Sb, Ba-Ga-Sb, and Ba-In-Sb." Phd thesis, 2014. https://tuprints.ulb.tu-darmstadt.de/4300/1/Thesis.pdf.
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Zintl phases have attracted interest due to their physical properties, electronic and crystal structures. In recent years ternary Zintl phases were being studied for their interesting thermoelectric properties. Though many Zintl phases are known, the compounds discussed in this work were not studied extensively before. This work emphasizes ternary Zintl phases containing barium and antimony. Ba3AlSb3, Ba3GaSb3, Ba7Ga4Sb9, BaGa2Sb2, and Ba5In2Sb6 have been investigated. In this work, ternary Zintl phases were prepared with optimized synthetic routes and characterized. DFT was used to calculate band gaps, according to which Ba3AlSb3 and Ba3GaSb3 are expected to be semiconductors and Ba7Ga4Sb9, BaGa2Sb2 and Ba5In2Sb6 should be metallic.
Spark plasma sintering was used to compact the products of high-temperature reactions of the elements to make pellets for thermoelectric measurements. Ba3AlSb3 exhibits high Seebeck coefficients (αmax = 383 µVK-1 at 342 K), low electrical (σmax = 18 Sm-1 at 342 K) and thermal conductivities (Κmin = 0.75 Wm-1K-1 at 342 K). Ba3GaSb3 also shows high Seebeck coefficients, low electrical and thermal conductivities. ZT values of both compounds were found to be low due to very low electrical conductivities. To modify the properties doping was attempted using zinc, calcium and strontium as dopants. The products were analysed to identify the presence of dopants using energy dispersive X-ray spectroscopy and atomic absorption spectroscopy. As an example, the thermoelectric properties of Ba3Al0.97Zn0.03Sb3 were studied. It shows modified properties and a higher figure of merit (ZTmax = 0.1081 at 490 K) than the undoped Ba3AlSb3. The thermoelectric properties of Ba7Ga4Sb9 could not be studied due to lack of thermal stability. BaGa2Sb2 was found to be stable in air. It shows high Seebeck coefficients, low electrical and thermal conductivities. Ba5In2Sb6 was found to be an n-type semiconductor. Ba5In2Sb6 exhibits low Seebeck coefficients (αmin = -74 µVK-1 at 473 K), low electrical (σmax = 12,955 Sm-1 at 683 K) and thermal conductivities (Κmin = 1.73 Wm-1K-1 at 520 K). The ZT values of BaGa2Sb2 and Ba5In2Sb6 were also found to be low.
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Cristea, Peter [Verfasser]. "Molekularstrahlepitaxie im Materialsystem Ga(N,Sb) / vorgelegt von Peter Cristea." 2002. http://d-nb.info/965611817/34.
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Jen, I.-Lun, and 任毅倫. "Phase diagram of ternary Zn-Sb-Ga system and Thermoelectric properties of Ga doped Zn4Sb3 alloys." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/5wu289.
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碩士國立中山大學
材料與光電科學學系研究所
107
In order to cope with the global warming and energy sustainability, the development of thermoelectric (TE) materials has grown extremely in recent years. The p-type β-Zn4Sb3 attracts great attention in the application of middle temperature thermoelectric generators.The addition of Gallium (Ga) in the Zn4Sb3 leads to the power factor (PF) increasing with two times in selective Ga-doped Zn4Sb3 which is grown crystal by the Bridgman method. At 623 K, the maximum solubility of Gallium in Zn4Sb3 under the thermally equilibrium state is less than 4 at.%Ga, as suggested by the isothermal section of ternary Zn-Sb-Ga system. As a result, the Ga-substituted (Zn1-xGax)4Sb3 achieves high figure of merit zT of 1.36 at 673 K as a result of the reduced κ~0.70 (W/mK) and enhanced PF~1.3 (mW/mk2) compared with the undoped Zn4Sb3 (zT~0.8), showing an ideal demonstration of phonon-glass-electron-crystal (PGEC).
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Shih, Pao-Chuan, and 施保全. "High-Performance In(Ga)As/Ga(As)Sb Heterojunction Tunneling Devices for Steep-Subthreshold-Slope Applications." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/79567521259975104511.
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碩士國立臺灣大學
電子工程學研究所
105
Tunneling field-effect transistor is a promising candidate for the nextgeneration digital switch due to the steep subthreshold slope (SS) of sub-60 mV/decade. Since the small drive current is still an issue for group IV TFETs, due to the small direct bandgap and effective mass, high-performance TFETs have been demonstrated by InGaAs/GaAsSb and InAs/GaSb heterojunctions. To investigate the current capability of tunneling from the heterojunctions, InAs/GaSb heterostructure were grown and the tunneling diodes were fabricated. By scaling down the device size, negative differential resistance was observed with a high peak tunneling current density of 32 MA/cm2 and a reverse-biased band-to-band tunneling (BTBT) current density of 26 MA/cm2 at -0.5 V. Furthermore, low-temperature measurement results and theoretical calculation confirm that the BTBT is the dominate current mechanism. While III/V TFETs of high performance were demonstrated, the large OFF leakage and poor SS are still critical issues. We propose a vertical TFET structure of BTBT direction aligned with the gate electric field and the operation were characterized by TCAD. ON and OFF current could be separately controlled by the insertion of a spacer layer. Simulation results show that for In(Ga)As/Ga(As)Sb heterojunction TFETs, the drive current can be as high as 1500 A/m at Vds = 0.3 V with a Ion/Ioff of 107. The best SS is 3 mV/decade with an average swing of 8 mV/decade over 5 decades of the drive current. To prove the concept of proposed vertical TFETs, Si/SiGe heterojunction TFETs were epitaxially grown and fabricated due to the cost consideration. A subthreshold swing of 800 mV/decade was achieved with a Ion/Ioff ratio of 1,000. While the device performance is far from ideal, the experimental results did show the potentials of the proposed vertical structure.
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Graf, Nikolaus Johannes Hubertus [Verfasser]. "Molekularstrahlepitaxie in den Mischsystemen Ga(Sb,Bi) und In(Sb,Bi) / vorgelegt von Nikolaus Johannes Hubertus Graf." 2008. http://d-nb.info/990742350/34.
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Liao, Yung-da, and 廖詠達. "Study on co-evaporation process of Cu(In,Ga)Se2 with Sb." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/05174020856054296835.
Full textAbstract:
碩士國立中山大學
材料與光電科學學系研究所
100
The study focus on low temperature process with doping antimony to refine the quality of the CI(G)S thin film, and doping gallium to increase energy band gap in two-stage co-evaporation process. Furthermore, we discuss about the variety of crystal structure, and recognize the value of energy band gap in transmission spectra. It has been achieved to increase the energy band gap of material with doping gallium. Recognizing the shift of XRD pattern and research result from papers, I estimate the content ratio of gallium in ⅢA atoms is 0.28~0.29, near my establishment ratio 0.3. By tuning the molecular beam flux of antimony effusion cell from 1.1×1013 atoms/cm2second to 2.2×1014 atoms/cm2second , to find out the property content of antimony involving of co-evaporation to optimize the quality of the CI(G)S polycrystalline thin film. We just observed that the thin film with antimony involving make effect of smoother and denser surface morphology. In our study, we also try discontinue supplying the antimony vapor to reduce the amount of antimony which involves the reaction process, and make low content of antimony leaved in the CI(G)S thin film. Here, We found out a special effect of the grain- growth of the CI(G)S thin film supplying antimony continually or not in the process. It should be strong (112) prefer orientation when we deposit the thin film using SLG substrate. However, we found out that antimony enhance the (220/204) .
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Shen, Jun. "Untersuchungen in ternären chalkogenhaltigen Systemen Ag-Ga-Te und Sn-Sb-Se." Doctoral thesis, 2003. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2003021919.
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Chalkogensysteme gewinnen aufgrund der halbleitenden Eigenschaften immer mehr an Bedeutung und sind Ziel technischer Anwendungen. Die Aufklärung der Phasengleichgewichte binäreren und ternäreren Chalkogensystemen sind für diesen Forschungszweig von besonderem Interesse. Einen wichtigen Beitrag zur Aufklärung der Phasengleichgewichte liefert die Bestimmung thermodynamischer Daten und die experimentellen Untersuchungen von Zustandsdiagrammen. Reaktivitätsuntersuchungen der intermetallischen und chalkogenhaltigen Verbindungen führen zu neuen Kenntnissen zum Reaktionsverhalten schwerzugängiger Verbindungen. Um eine schnelle und phasenreine Herstellung zu erzielen, kann die mechanische Synthese angewandt werden. Ein anderer Aspekt zur Synthese liegt auf dem Gebiet der Strukturanalyse von Chalkogenidometallaten. Mittels Hydrothermalsynthese werden verschiedene organische Template als Reaktionspartner eingesetzt, um neue Strukturen zu entdecken. Im Rahmen dieser Arbeit wurden Differenz-Thermoanalyse und röntgenographische sowie mikroanalytische Methoden und mikroskopische Gefügeuntersuchungen an den chalkogenhaltigen ternären Systemen Silber-Gallium-Tellur und Zinn-Antimon-Selen durchgeführt.
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錢元俊. "Phase equilibria isothermal section and liquidus projection of thermoelectric Co-Sb-Ga alloys." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/47618064835598764992.
Full textAbstract:
碩士國立清華大學
化學工程學系
101
CoSb3 is an important thermoelectric material. Recent studies indicate that Ga alloying in CoSb3 could further improve its figure of merit, zT. The Co-Sb-Ga ternary system is thus of high interests for thermoelectric applications. Phase diagrams are fundamental for understanding of phase transformation and materials microstructures, which are closely related to the materials thermoelectric properties. Phase diagrams are thus crucial for development of thermoelectric materials. The Co-Sb-Ga liquidus projection and the 650℃ Co-Sb-Ga phase equilibria isothermal section are constructed in this study. As-cast Co-Sb-Ga alloys were prepared, and their primary solidification phases were determined. The Co-Sb-Ga liquidus projection was constructed based on the experimental results of primary phases, and the phase diagrams of its three constituent binary systems. The primary solidification phases are the three terminal solid solution phases, six binary compounds: CoGa, CoGa3, GaSb, CoSb3, CoSb2, CoSb and a ternary compound- Co3Sb2Ga4 which has not been reported before; Ternary Co-Sb-Ga alloys equilibrated at 650℃ as well. The equilibrium phases and their compositions were determined. Four three-phase regions and one two-phase region have been determined. The liquidus projection and the 650℃ isothermal section were also calculated using Calphad method. Both experimental determinations and the calculated results are qualitatively in good agreement.
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HUANG, CHONG-GUI, and 黃崇桂. "Liquid-phase-epitaxial(LPE) growth of Alx Ga(1-x)Sb and surface characterizations." Thesis, 1988. http://ndltd.ncl.edu.tw/handle/85549817562446261475.
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碩士國立成功大學
物理研究所
76
AlxGa(1-x)Sb半導體其能隙隨ｘ值不同而從０．７eV改變至１．４eV，此種材料在光 電元件上之應用有極大的潛力。 本文討論以液相磊晶（LPE ）技術中的超冷降溫法於銻化鎵基片上成長三種不同組成 的AlxGa(1-x)Sb，利用SEM （Scanning Electron Mircoscopy），EDAX（Energy Dis persion Analysis X-ray），測量磊晶層的特性並得到成長過程的最佳溫度曲線。Ｘ ＝０．１２的樣品表面經１：１的鹽酸和甲醇處理得可得如鏡面般的平坦，從剖面的 SEM 相片中得知鋁之莫耳分率愈高時成長速率愈慢。經XPS（X-ray Photolectron Sp ectroscopy）的測量結果指出磊晶的表面是以氧化狀態存在。由PL（Photoluminesce nce） 的測試得知在不同組成下能隙的大小分別為Ｘ＝０．０６時Ｅg ＝０．８５eV ，Ｘ＝１．１２４，Ｅg ＝０．９０８eV；Ｘ＝０．１２８，Ｅg ＝０．９１２eV； Ｘ＝０．２４２，Ｅg ＝１．０３１eV，銻化鎵的Ｅg ＝０．８eV。
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Chang, Hsiao-wen, and 張曉文. "Electric-Field Effects on Magnetic Properties of (Ga,Mn)Sb Channel in Field-Effect Structures." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/f3572j.
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博士國立中山大學
物理學系研究所
103
This thesis investigates the magnetotransport properties of ultrathin (Ga,Mn)Sb layers in a field-effect structure. We fabricate a metal-insulator-semiconductor field-effect structure with a thin (Ga,Mn)Sb channel and investigate its magnetotransport properties, as functions of temperature, external magnetic field, and gate electric field. The results show that one can control magnetic properties of (Ga,Mn)Sb by applying electric fields, as similar to (Ga,Mn)As. The most prominent finding is that the Curie temperature of (Ga,Mn)Sb can be modulated by gating but in somewhat different manner from (Ga,Mn)As. For (Ga,Mn)Sb, we determine experimentally the relationship between the Curie temperature TC and hole concentration p, to be Tc ∝ p^ϒ with ϒ of 1.3~1.6, which is several times larger than ϒ ~ 0.2 reported previously for (Ga,Mn)As. We show that the value of ϒ can be reproduced by the numerical calculations based on the adapted p-d Zener model with non-uniform hole distribution, and the calculation indicates the accumulation of holes in (Ga,Mn)Sb in the vicinity of the interface with a gate insulator, while for (Ga,Mn)As the depletion of holes at the interface. The results are consistent with the reported Fermi energy pinning positions for p-GaSb and p-GaAs. We also find that the conductivity dependence of the Hall conductivity is different from that reported for (Ga,Mn)As. The findings are of great importance for employing thin and ultrathin layers of (Ga,Mn)Sb or related compounds in the concept of spintronics devices, where magnetic and electronic properties are mutually controlled.
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Shen, Jun [Verfasser]. "Untersuchungen in ternären chalkogenhaltigen Systemen Ag-Ga-Te und Sn-Sb-Se / eingereicht von Jun Shen." 2001. http://d-nb.info/97038033X/34.
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Lee, Chain-Ming, and 李乾銘. "Structure, Crystallization Kinetics and Optical Properties of Chalcogenide Phase Change Media Based on Ga-Sb-Te." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/27115809510605170928.
Full textAbstract:
博士國立清華大學
材料科學工程學系
91
Physical properties of the chalcogenides based on GaSbTe system were investigated and their feasibility as phase-change recording media was also evaluated. Thin films of compositions between the Sb7Te3-GaSb and Sb2Te3-GaSb pseudo-binary tielines were prepared by an RF co-sputtering method. The laser-crystallized structures of the GaSbTe films were identified by X-ray diffraction. All the crystallized films show rhombohedral structures of space group R-3m with continuous variation in lattice constants. The model of six-layer hexagonal lattice was proposed. The crystallization kinetics of amorphous GaSbTe powders and films were studied by non-isothermal differential scanning calorimetry (DSC) and isothermal time-resolved transmission, respectively. In DSC studies, the crystallization temperature and activation energy increase with increasing GaSb content. The kinetic exponents confirm the crystallization mechanism to be diffusion-controlled growth with decreased nucleation and show higher values at the SbTe-rich compositions. In transmission studies, crystallization of GaSbTe films reveals the two-step feature: initial surface nucleation and coarsening followed by one-dimensional grain growth. The kinetic parameters of the first stage show much correspondence with those of non-isothermal cases. Optical properties of amorphous and crystalline GaSbTe films were analyzed by a spectrometer and ellipsometry. The optical spectra of binary SbTe films show higher reflectance and lower absorptance at the crystalline state, while that of GaSb film shows the reverse case. Compositional deviation from binary SbTe to GaSb reduces the reflectivity ratio between crystalline and amorphous states but increases the absorption ratio instead. The changes in optical spectra can be interpreted in terms of the optical constants, and more explicitly, the optical bandgaps. The addition of GaSb into binary SbTe tends to diminish the changes in peak amplitudes and peak locations of both n and k values during the phase transformation, leading to lower optical contrast. The absorption coefficients of all studied films reveal allowed indirect optical transitions at either amorphous or crystalline state. After crystallization, the optical bandgaps of amorphous films are greatly reduced. Phase-change recording disks based on the GaSbTe recording media were prepared in the DVD+RW format and evaluated by a dynamic tester. Enhanced recrystallization has been demonstrated in the disks with Sb7Te3-rich recording layer, and the approximated composition Ga2Sb5Te3 exhibits a nearly complete erasure (-40 dB). Relationship between dynamic characteristics and lattice constants of the GaSbTe recording media has been proposed.
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Chen, Wei-an, and 陳韋安. "Ni/CoSb3 interfacial reactions and CoSb3-GaSb isoplethal section in the Co-Sb-Ga ternary thermoelectric material system." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/04260235710889409887.
Full textAbstract:
碩士國立清華大學
化學工程學系
102
Energy is among the most critical sustainability issues for human beings due to the rapid growth of world population. However, the energy usage is not efficient and there is a very high percentage of waste heat. Thermoelectric device can convert waste heat directly into electricity, and has attracted a lot of attention and research interests. There are two main subjects in the thermoelectric device development. One is finding materials with better thermoelectric properties, and the other is improving the reliability and enhancing the durability of thermoelectric devices. Focusing on these two subjects, this study determines the Co-Sb-Ga phase equilibria and Ni/CoSb3 interfacial reactions. CoSb3 is a promising thermoelectric material and has a unique skutterudite structure. It has been reported that doping Ga into CoSb3 can reduce its lattice thermal conductivity and significantly enhance its ZT value. One kind of phase diagram of the Co-Sb-Ga ternary system, the CoSb3-GaSb isoplethal section, is determined in this study. This isoplethal section has 9 phase regions which are CoSb+Liquid, CoSb+CoSb2+Liquid, CoSb2+Liquid, CoSb2 +CoSb3+Liquid, CoSb3+Liquid, CoSb3+GaSb +Liquid, GaSb+Liquid, CoSb3+GaSb and Liquid. The joints in thermoelectric devices are also very important. Diffusion barrier is usually introduced between solder and thermoelectric material to prevent their inter-diffusion. Nickel is a common diffusion barrier layer. The interfacial reactions in the Ni/Sb and Ni/CoSb3 couples at 450oC are examined. Three intermetallic phases are formed in the Ni/Sb couple, and the phases in the couple are Ni/Ni5Sb2/NiSb/NiSb2/Sb. The reaction layer becomes thicker with longer reaction time, and it is 27μm after reaction for 24 hours. The NiSb2 phase is not observed in the Ni/CoSb3 couple reacted at 450oC up to 20 hours, and the phases observed are Ni/Ni5Sb2/(Ni,Co)Sb/CoSb3. The thickness of reaction layer is 22 μm after 20 hour-reaction at 450oC. It is concluded that Nickel is the fastest diffusion species.
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Liu, Chun-Kuan, and 劉俊寬. "Effect of the Ga/Sb Treatment on the Growth of GaSb Epitaxy on GaAs Substrate Using Metalorganic Chemical Vapor Deposition." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/gc8feq.
Full textAbstract:
碩士國立交通大學
光電系統研究所
104
In recent years, due to scaling down of the semiconductor manufacturing process, traditional MOSFET will meet the problem of gate leakage current. In order to solve this problem, it is needed to introduce new materials and new device structures. Antimonide based tunneling FET may be one of the solution in the future. However, lattice mismatch between antimonide and commercial GaAs wafer is too large, it is very important to overcome the strain and defects that produced due to lattice mismatch. In this study, direct growth of GaSb on GaAs substrate has been investigated. Effects of GaSb/GaAs interfacial treatment parameters on the GaSb initial growth mode has been discussed in this work. By modulating TMGa flux and flow time, TMSb flux and flow time, we got the information of the vertical/lateral growth ratio of GaSb island. We discovered that when we use TMSb as interfacial treatment, it effectively lowers the surface free energy and promotes lateral growth mode of GaSb growth. By optimizing TMSb interfacial treatment, we can get 75 nm high quality GaSb thin film with surface roughness 1.7 nm and FWHM of XRD rocking curve is 371 arcsec.
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Jayaganthan, R. "Experimental Investigations And Thermodynamic Modelling Of Selected III-V Semiconductor Alloys." Thesis, 1997. http://etd.iisc.ernet.in/handle/2005/1852.
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Acharya, Sibasis. "Thermodynamics And Phase Equilibria In The Systems Involving Electronic Materials." Thesis, 2004. http://etd.iisc.ernet.in/handle/2005/1300.
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Ni, Jun-Long, and 倪俊龍. "Determination of Ga,Ge,As,Se and Sb in coal fly ash and S and Pb in gasoline by inductively coupled plasma mass spectrometry." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/43591702728253410756.
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Ganesan, K. "Growth, Structural And Physical Properties Of Certain Antimony Based III-V Diluted Magnetic Semiconductors." Thesis, 2008. http://hdl.handle.net/2005/773.
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Semiconductor devices are the building blocks of electronics and communication technology in the modern world. The charge, mass and spin of charge carriers in the semiconductor devices lay the foundations of the technology developments in the modern age. But to date only the electronic charge of the semiconductors has been exploited for such applications. The significance of the spin of charge carriers is completely ignored because in a semiconductor the half of the carriers are in spin-up state and the remainder are in spin-down state. A new electronics termed as spintronics, spin-transport based electronics, is focused to utilise the spin degree of freedom of the charge carriers in addition to its electronic charge. The devices based on these have the potential for various technological advancements like non-volatility, increased data processing speed, decreased electronic power consumption and increased integration densities as compared to the conventional semiconductor devices. In this study, the author intended to study the growth and properties of magnetic impurity doped antimony based III-V compounds and compare these results with those of the films grown by MBE.
This thesis is organised into seven chapters. The first introductory chapter gives a brief review of the work on spintronics, diluted magnetic semiconductors, Ferromagnetic / paramagnetic semiconductor hybrid structures with special emphasis on the properties of antimonides which have already been reported in the literature. This is followed by the scope of the thesis. The second chapter deals with technical details of various instruments used in the present research work.
Third chapter describes the growth and structural properties of bulk crystals grown by Bridgman method and thin films grown by liquid phase epitaxy (LPE). Bulk crystals of InSb and GaSb doped with magnetic elements such as Mn and Fe are grown with different doping concentrations. Thin films of InSb and GaSb doped Mn with different doping concentrations are grown by LPE. The grown crystals are processed by slicing, lapping, polishing and chemical etching methods. X-ray diffraction studies are carried out to confirm alloy formation and to find the change in lattice parameter if any. From the powder diffraction patterns, the lattice parameter is refined with the help of Retvield refinement program. A systematic change of lattice parameter with the incorporation of magnetic impurities into InSb and GaSb is observed. Scanning electron microscopy and energy dispersive x-ray analysis are carried out to identify the secondary phases and their composition respectively.
Chapter 4 gives the detailed magnetotransport studies carried out on InSb and GaSb crystals doped with Mn and Fe. Also, the magnetotransport studies carried out on thin films grown by liquid phase epitaxy are presented here. This chapter is divided into three sections of which the first section deals with Mn doped bulk crystals of InSb and GaSb, the second section deals with Fe doped bulk crystals of InSb and GaSb and the third section deals with Mn doped InSb and GaSb films grown on GaAs by Liquid Phase Epitaxy. Temperature dependence of zero field resistivity, magnetoresistance and Hall measurements are carried out from 1.4 to 300K. All the samples show p type conduction throughout the temperature range studied except for Fe doped InSb. Mn doped crystals show negative magnetoresistance and anomalous Hall effect below 10K. Anisotropy in magnetoresistance is also observed at low temperatures in InMnSb crystals. On the other hand, Fe doped samples exhibit positive magnetoresistance throughout the temperature range and no anomalous Hall effect is observed.
Chapter 5 describes the magnetic properties of bulk InMnSb, GaMnSb, InFeSb and GaFeSb crystals so also the thin films of InMnSb/GaAs. DC magnetization measurements are carried out in the temperature range 2 - 300K. The Mn doped InSb and GaSb crystals as well as InMnSb/GaAs films, show a magnetic ordering below 10K which could arise from the InMnSb and GaMnSb alloy formation. Also, saturation in magnetization observed even at room temperature suggests the existence of ferromagnetic MnSb clusters in the crystals which has been verified by scanning electron microscopy studies. In Fe doped InSb crystals, the temperature dependent DC magnetization shows irreversibility under field cooled and zero field cooled conditions below 12K, suggesting a spin glass-like behaviour. Also, magnetization measurement shows the coexistence of ferromagnetic and paramagnetic phases throughout the temperature range studied. Existence of ferromagnetic phase could arise from secondary phases Fe1-xInx or FeSb2 present in the crystal as clusters and paramagnetic phase could arise from the randomly distributed Fe atoms in the InSb matrix. Fe doped GaSb crystals show interesting magnetic property that arises from the FeGa alloy (secondary phase) present in it. The EPR studies on Ga0.98Mn0.02Sb cluster-free (?) crystal suggest that the dominant Mn impurity in GaMnSb is Mn2+ (d5), described as ionized acceptor A−. This conclusion was derived from EPR experiments, which reveal a strong absorption line with an effective g factor very close to 2.00, the value typical for centre A−. The absence of EPR signal typical for neutral Mn acceptor A0 suggests that this center is absent in the crystal under investigation. The observed behavior is similar to that of Ga1-xMnxAs and In1-xMnxAs epilayers. EPR studies also reveal that the competition between antiferromagnetic and ferromagnetic phases exists in the studied crystal.
Chapter 6 describes the optical measurements carried out on bulk Ga1-xMnxSb crystals and their films with different Mn doping concentrations. FTIR studies are carried out in the temperature range 4 - 300 K. From the FTIR studies, it is found that intra valance spin – orbit splitting band absorption is dominant compared to the fundamental absorption in doped crystals. In higher doped crystals (x > 0.01), fundamental band absorption merges with split-off band and could not be resolved. Free carrier absorption studies are also carried out in the energy range below the band gap. FTIR studies on GaMnSb/GaAs films suggest band gap narrowing effect due to Mn doping. Furthermore the Photoluminescence measurements are carried out in the temperature range 10 – 300 K for all the Mn doped GaSb crystals. PL studies also support the band gap narrowing and band filling effects.
A comprehensive summary of this research investigation and scope for the further work are presented in the last chapter.
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Gélinas, Guillaume. "Comprendre et maîtriser le passage de type I à type II de puits quantiques d'In(x)Ga(1-x)As(y)Sb(1-y) sur substrat de GaSb." Thèse, 2015. http://hdl.handle.net/1866/16034.
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Les antimoniures sont des semi-conducteurs III-V prometteurs pour le développement de dispositifs optoélectroniques puisqu'ils ont une grande mobilité d'électrons, une large gamme spectrale d'émission ou de détection et offrent la possibilité de former des hétérostructures confinées dont la recombinaison est de type I, II ou III. Bien qu'il existe plusieurs publications sur la fabrication de dispositifs utilisant un alliage d'In(x)Ga(1-x)As(y)Sb(1-y) qui émet ou détecte à une certaine longueur d'onde, les détails, à savoir comment sont déterminés les compositions et surtout les alignements de bande, sont rarement explicites. Très peu d'études fondamentales sur l'incorporation d'indium et d'arsenic sous forme de tétramères lors de l'épitaxie par jets moléculaires existent, et les méthodes afin de déterminer l'alignement des bandes des binaires qui composent ces alliages donnent des résultats variables.
Un modèle a été construit et a permis de prédire l'alignement des bandes énergétiques des alliages d'In(x)Ga(1-x)As(y)Sb(1-y) avec celles du GaSb pour l'ensemble des compositions possibles. Ce modèle tient compte des effets thermiques, des contraintes élastiques et peut aussi inclure le confinement pour des puits quantiques. De cette manière, il est possible de prédire la transition de type de recombinaison en fonction de la composition.
Il est aussi montré que l'indium ségrègue en surface lors de la croissance par épitaxie par jets moléculaires d'In(x)Ga(1-x)Sb sur GaSb, ce qui avait déjà été observé pour ce type de matériau. Il est possible d'éliminer le gradient de composition à cette interface en mouillant la surface d'indium avant la croissance de l'alliage. L'épaisseur d'indium en surface dépend de la température et peut être évaluée par un modèle simple simulant la ségrégation. Dans le cas d'un puits quantique, il y aura une seconde interface GaSb sur In(x)Ga(1-x)Sb où l'indium de surface ira s'incorporer. La croissance de quelques monocouches de GaSb à basse température immédiatement après la croissance de l'alliage permet d'incorporer rapidement ces atomes d'indium et de garder la seconde interface abrupte.
Lorsque la composition d'indium ne change plus dans la couche, cette composition correspond au rapport de flux d'atomes d'indium sur celui des éléments III. L'arsenic, dont la source fournit principalement des tétramères, ne s'incorpore pas de la même manière. Les tétramères occupent deux sites en surface et doivent interagir par paire afin de créer des dimères d'arsenic. Ces derniers pourront alors être incorporés dans l'alliage. Un modèle de cinétique de surface a été élaboré afin de rendre compte de la diminution d'incorporation d'arsenic en augmentant le rapport V/III pour une composition nominale d'arsenic fixe dans l'In(x)Ga(1-x)As(y)Sb(1-y). Ce résultat s'explique par le fait que les réactions de deuxième ordre dans la décomposition des tétramères d'arsenic ralentissent considérablement la réaction d'incorporation et permettent à l'antimoine d'occuper majoritairement la surface. Cette observation montre qu'il est préférable d'utiliser une source de dimères d'arsenic, plutôt que de tétramères, afin de mieux contrôler la composition d'arsenic dans la couche.
Des puits quantiques d'In(x)Ga(1-x)As(y)Sb(1-y) sur GaSb ont été fabriqués et caractérisés optiquement afin d'observer le passage de recombinaison de type I à type II. Cependant, celui-ci n'a pas pu être observé puisque les spectres étaient dominés par un niveau énergétique dans le GaSb dont la source n'a pu être identifiée. Un problème dans la source de gallium pourrait être à l'origine de ce défaut et la résolution de ce problème est essentielle à la continuité de ces travaux.Antimonide-based semiconductors are promising in the development of optoelectronic devices considering that the high electron mobility, the possibility to emit or absorb light for a large number of wavelengths in the infrared region and the change in recombination type for confined heterostructure make them a prime subject of research. A good number of publications are aimed at developing devices based on In(x)Ga(1-x)As(y)Sb(1-y) alloys to emit or detect a specific wavelength without giving much information about the composition determination or the band alignment. There are only a few fundamental studies about the incorporation of indium and none about the incorporation of arsenic tetramers by molecular beam epitaxy. Also, the values of the band offsets between binary compounds forming the In(x)Ga(1-x)As(y)Sb(1-y) alloys diverge and the methods used to do so are sometimes arbitrary. A model was constructed and predicts the band alignment between In(x)Ga(1-x)As(y)Sb(1-y) alloys and GaSb for any values of x and y. This model considers thermal effects, strain and confinement for quantum wells. Therefore, it is possible to predict the type of recombination for any composition. Indium atoms tend to segregate on the surface while the growth of In(x)Ga(1-x)Sb on GaSb is taking place by molecular beam epitaxy. This behavior has already been seen before and the work presented here corroborates this observation. It is possible to build up a thin layer of indium on the surface prior to the growth of the alloy to avoid a change of composition in the layer. The thickness of this layer is dependent on the temperature of the substrate and can be evaluated with a simple model of segregation. In the case of a quantum well, there will be another interface where the indium floating on the surface will incorporate. To avoid the formation of a long gradient of composition at this interface, it is recommended to grow a few monolayers of GaSb at low temperature without a growth interruption. This way, the indium will incorporate rapidly and leave a sharp interface. The ratio between the indium beam equivalent pressure and the beam equivalent pressure of indium and gallium gives the nominal composition and is the same as the measured composition by XRD in the alloy. The incorporation of arsenic tetramers is not as straightforward in In(x)Ga(1-x)As(y)Sb(1-y) alloys and is shown to decrease when the V/III ratio is increased as measured by XRD. A simple kinetic model explained that this behavior is caused by antimony occupying a large fraction of the surface. The dissociation of tetramers into dimers is a reaction of second order and the tetramers occupy two sites on the surface and makes the incorporation a slower process. Therefore, the use of arsenic tetramers is not the best choice for a good control on the arsenic composition in the layer. In(x)Ga(1-x)As(y)Sb(1-y) quantum wells were grown on GaSb and were optically characterized to observe the transition of type I recombination to type II. This transition could not be corroborated because all the measurements showed an unknown transition related to the GaSb buffer layer. The origin of this optical signature could not be identified, but may be related to a contaminant in the gallium cell. Identifying the source of this problem and solving it will be essential to go further and observe the transition of type I to type II.