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1
McQuaid, Seamus A. "The high electron mobility transistor." Thesis, University of Manchester, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293300.
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Chen, Jr-Tai. "MOCVD growth of GaN-based high electron mobility transistor structures." Doctoral thesis, Linköpings universitet, Halvledarmaterial, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-117138.
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The present work was to improve the overall quality of GaN-based high electron mobility transistor (HEMT) epitaxial structures grown on semi-insulating (SI) SiC and native GaN substrates, using an approach called bottom-to-top optimization. The bottom-to-top optimization means an entire growth process optimization, from in-situ substrate pretreatment to the epitaxial growth and then the cooling process. Great effort was put to gain the understanding of the influence of growth parameters on material properties and consequently to establish an advanced and reproducible growth process. Many state-of-the-art material properties of GaN-based HEMT structures were achieved in this work, including superior structural integrity of AlN nucleation layers for ultra-low thermal boundary resistance, excellent control of residual impurities, outstanding and nearly-perfect crystalline quality of GaN epilayers grown on SiC and native GaN substrates, respectively, and record-high room temperature 2DEG mobility obtained in simple AlGaN/GaN heterostructures. The epitaxial growth of the wide bandgap III-nitride epilayers like GaN, AlN, AlGaN, and InAlN, as well as various GaN-based HEMT structures was all carried out in a hot-wall metalorganic chemical vapor deposition (MOCVD) system. A variety of structural and electrical characterizations were routinely used to provide fast feedback for adjusting growth parameters and developing improved growth processes.
3
Zhao, Xu S. M. Massachusetts Institute of Technology. "Electric field engineering in GaN high electron mobility transistors." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/43062.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2008.Includes bibliographical references (leaves 66-70).
In the last few years, AlGaN/GaN high electron mobility transistors (HEMTs) have become the top choice for power amplification at frequencies up to 20 GHz. Great interest currently exists in industry and academia to increase the frequency to mm-wave frequencies. The goal of this thesis has been to identify new solutions to some of the main challenges to increase this frequency performance even further. Electron velocity is a critical parameter affecting the transistor performance. In standard GaN transistors, the extremely high electric fields present in the channel of the device reduce the average electron velocity well below the peak electron velocity, resulting in low cutoff frequencies. In this thesis, we introduced a partial recess in the drain access region of the transistor to engineer the electric field along the channel of the device without introducing parasitic capacitances. By reducing the peak electric field, the average electron velocity is increased by 50%. This new technology has the potential to improve not only the cutoff frequencies, but also the breakdown voltage of GaN transistors. To successfully engineer the electric field in GaN devices, an accurate, reliable and low damage etching technology is needed. However none of the traditional GaN dry etching technologies meets these requirements. This lack of suitable technology has motivated us to develop a new atomic layer etching technique of AlGaN/GaN structures. This technology has been shown to be a self limited process with very high reliability and low damage, which will be very useful both in electric field engineering and gate recess. Finally, another factor hindering GaN HEMTs from competing with InGaAs devices at high frequencies are their high parasitic capacitances and resistances. In this thesis, ohmic drain contacts are replaced with Schottky drain contacts to reduce the drain access resistance.
(cont) ADS simulations predict a very significant increase in the cutoff frequencies by virtue of the lowered parasitic resistances. In conclusion, the theoretical and experimental work developed during this project has demonstrated the great potential of three new technologies to overcome the main challenges of mm-wave GaN HEMTs. The application of these technologies to actual devices is under way and it will represent an important element of the ultra-high GaN transistors of the future.
by Xu Zhao.
S.M.
4
Yu, Tsung-Hsing. "Numerical studies of heterojunction transport and High Electron Mobility Transistor (HEMT) devices." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/13035.
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ISLAM, MD SHAHRUL. "Can Asymmetry Quench Self-Heating in MOS High Electron Mobility Transistors?" OpenSIUC, 2020. https://opensiuc.lib.siu.edu/theses/2736.
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High electron mobility transistors (HEMTs) have long been studied for high frequency and high-power application. Among widely known high electron mobility transistors, AlGaN/GaN HEMTs are having the upper hand due to high electron mobility of the GaN channel. Over the times, issues like current collapse, gate leakage, self-heating and gate lag have questioned the performance and reliability of these devices. In the recent years, engineers have come up with newer architectures to address some of these issues. Inserting a high-k dielectric oxide layer in the gate stack proved to be an effective solution to mitigate gate leakage, reduce interfacial traps and improve optimal working conditions. This work aims to study the reliability aspect of these so-called metal-oxide-semiconductor high electron mobility transistors (MOS-HEMT) specifically, HfO2 and HfZrO2 MOS-HEMTs. It was found through numerical simulations that though HfO2 and HfZrO2 dielectrics were able to mitigate gate leakage current, they tend to accumulate more heat in the channel region with respect to the conventional silicon nitride (SiN) passivated counterparts. Moreover, few asymmetric structures were proposed where silicon nitride was placed in the dielectric layer along with HfO2/HfZrO2. In this study it was found that these asymmetric structures showed superior thermal performance while showing near-zero gate leakage current.
6
Holmes, Kenneth L. "Two-dimensional modeling of aluminum gallium nitride/gallium nitride high electron mobility transistor." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02Jun%5FHolmes.pdf.
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Aminbeidokhti, Amirhossein. "Measurement and Analysis of Electron Mobility in GaN Power HEMTs." Thesis, Griffith University, 2016. http://hdl.handle.net/10072/368007.
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High-electron-mobility transistor (HEMT) is a promising device for power applications because of their high breakdown voltage, high electron mobility in two-dimensional electron gas (2DEG) area, fast switching capability, high-temperature operating capabilities, compatibility with standard electronic circuits, and low production cost.
In contrast to the gate in metal–oxide–semiconductor field-effect transistor (MOSFET), which extends from source to drain, the gate in HEMT splits the device into two main sections: field-effect (section under the gate) and resistive (section outside the gate). Resistances of the 2DEG outside the gate sections are constant and modelled by fixed resistors. However, the 2DEG resistance under the gate section is dependent to the gate voltage, which can be modelled by channel resistance of a field-effect transistor (FET). Since these resistances depend on the mobility of electrons in the 2DEG, it is important to separate the electron mobility in the resistive and field-effect sections. Therefore, existence of the resistive section in the HEMT structure leads to requiring new methods for the HEMT mobility measurement. Also, since there is no model for the HEMT in SPICE, novel models are required for the SPICE simulation of the HEMT. In order to solve these issues:Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
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Stevens, Lorin E. "Thermo-Piezo-Electro-Mechanical Simulation of AlGaN (Aluminum Gallium Nitride) / GaN (Gallium Nitride) High Electron Mobility Transistor." DigitalCommons@USU, 2013. http://digitalcommons.usu.edu/etd/1506.
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Due to the current public demand of faster, more powerful, and more reliable electronic devices, research is prolific these days in the area of high electron mobility transistor (HEMT) devices. This is because of their usefulness in RF (radio frequency) and microwave power amplifier applications including microwave vacuum tubes, cellular and personal communications services, and widespread broadband access. Although electrical transistor research has been ongoing since its inception in 1947, the transistor itself continues to evolve and improve much in part because of the many driven researchers and scientists throughout the world who are pushing the limits of what modern electronic devices can do. The purpose of the research outlined in this paper was to better understand the mechanical stresses and strains that are present in a hybrid AlGaN (Aluminum Gallium Nitride) / GaN (Gallium Nitride) HEMT, while under electrically-active conditions. One of the main issues currently being researched in these devices is their reliability, or their consistent ability to function properly, when subjected to high-power conditions. The researchers of this mechanical study have performed a static (i.e. frequency-independent) reliability analysis using powerful multiphysics computer modeling/simulation to get a better idea of what can cause failure in these devices. Because HEMT transistors are so small (micro/nano-sized), obtaining experimental measurements of stresses and strains during the active operation of these devices is extremely challenging. Physical mechanisms that cause stress/strain in these structures include thermo-structural phenomena due to mismatch in both coefficient of thermal expansion (CTE) and mechanical stiffness between different materials, as well as stress/strain caused by "piezoelectric" effects (i.e. mechanical deformation caused by an electric field, and conversely voltage induced by mechanical stress) in the AlGaN and GaN device portions (both piezoelectric materials). This piezoelectric effect can be triggered by voltage applied to the device's gate contact and the existence of an HEMT-unique "two-dimensional electron gas" (2DEG) at the GaN-AlGaN interface. COMSOL Multiphysics computer software has been utilized to create a finite element (i.e. piece-by-piece) simulation to visualize both temperature and stress/strain distributions that can occur in the device, by coupling together (i.e. solving simultaneously) the thermal, electrical, structural, and piezoelectric effects inherent in the device. The 2DEG has been modeled not with the typically-used self-consistent quantum physics analytical equations, rather as a combined localized heat source* (thermal) and surface charge density* (electrical) boundary condition. Critical values of stress/strain and their respective locations in the device have been identified. Failure locations have been estimated based on the critical values of stress and strain, and compared with reports in literature. The knowledge of the overall stress/strain distribution has assisted in determining the likely device failure mechanisms and possible mitigation approaches. The contribution and interaction of individual stress mechanisms including piezoelectric effects and thermal expansion caused by device self-heating (i.e. fast-moving electrons causing heat) have been quantified. * Values taken from results of experimental studies in literature
9
Ture, Erdin [Verfasser], and Oliver [Akademischer Betreuer] Ambacher. "GaN-based Tri-gate high electron mobility transistors." Freiburg : Universität, 2016. http://d-nb.info/1143602811/34.
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Joh, Jungwoo. "Degradation mechanisms of GaN high electron mobility transistors." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38670.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 83-85).
In spite of their extraordinary performance, GaN high electron mobility transistors (HEMT) have still limited reliability. In RF power applications, GaN HEMTs operate at high voltage where good reliability is essential. However, physical understanding of the fundamental reliability mechanisms of GaN HEMTs is still lacking today. In this thesis, we carry out systematic reliability experiments on industrial GaN HEMTs provided by our collaborators, TriQuint Semiconductor and BAE systems. In our study, GaN HEMTs have been electrically stressed at various bias conditions while they are being characterized by a benign characterization suite. We have confirmed that electrical stress on devices results in an increase in drain resistance RD and a decrease in maximum drain current IDmax. During the stress, traps are found to be generated. We have seen that this degradation is driven mostly by electric field, and current is less relevant to electrical degradation.
(cont.) From a set of our experiments, we have hypothesized that the main mechanism behind device degradation is defect formation through the inverse piezoelectric effect and subsequent electron trapping. Unlike current conventional wisdom, hot electrons are less likely to be the direct cause of electrical degradation in the devices that we have studied. Our studies suggest a number of possibilities to improve the electrical reliability of GaN HEMTs.
by Jungwoo Joh.
S.M.
11
Morton, Christopher Gordon. "The epitaxial layer design of HEMTs." Thesis, University of York, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261106.
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singh, Ranjit. "Characterisation and modelling of microwave high electron mobility transistors." Thesis, University of Leeds, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.702130.
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Lee, Kyoung-Keun. "Implementation of AlGaN/GaN based high electron mobility transistor on ferroelectric materials for multifunctional optoelectronic-acoustic-electronic applications." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28209.
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Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.Committee Chair: William. Alan Doolittle; Committee Member: Jeffrey Nause; Committee Member: Linda S. Milor; Committee Member: Shyh-Chiang Shen; Committee Member: Stephen E. Ralph.
14
Grémion, Emile. "Transistor balistique quantique et HEMT bas-bruit pour la cryoélectronique inférieure à 4. 2 K." Paris 11, 2008. http://www.theses.fr/2008PA112017.
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Pour augmenter la résolution globale des détecteurs à très basse température, aujourd'hui couramment utilisés dans de nombreux champs de la physique des particules et de l'univers, les expériences à venir ne pourront faire l'économie du développement d'une cryo-électronique performante, à la fois moins bruyante et plus proche du détecteur. Dans ce contexte, ce travail s'intéresse aux possibilités offertes par les gaz d'électrons bidimensionnels (2DEG) GaAlAs/GaAs à travers l'étude expérimentale de deux composants distincts : les QPC (Quantum Point Contact) et les HEMT (High Electron Mobility Transistor). En s'appuyant sur la quantification de la conductance dans les QPC, phénomène issu de la physique mésoscopique, un transistor balistique quantique fonctionnant à 4. 2 K a été réalisé. Le transport électronique à travers les bandes 1D permet d'obtenir un gain en tension supérieur à 1 avec une puissance dissipée d'environ 1 nW. En raison de leur très faible capacité d'entrée, ces dispositifs constituent également des candidats idéaux pour multiplexer des matrices de bolomètres haute impédance (collaboration DCMB). Les HEMT présentent des performances compatibles avec une utilisation à basse température, ayant une puissance dissipée de ~ 100 μW et un gain supérieur à 20. Le faible bruit en tension équivalent en entrée (1. 2 nV/Hz^(1/2) à 1 kHz et 0. 13 nV/Hz^(1/2) à 100 kHz) ouvre la voie à leur utilisation dans la lecture de détecteur de forte impédance. Conformément à la loi de Hooge, ces performances sont obtenues au détriment d'une capacité d'entrée élevée estimée à environ 60 pFNext generations of cryodetectors, widely used in physics of particles and physics of universe, will need in the future high-performance cryoelectronics less noisy and closer to the detector. Within this context, this work investigates properties of two dimensional electron gas GaAlAs/GaAs by studying two components, quantum point contact (QPC) and high electron mobility transistor (HEMT). Thanks to quantized conductance steps in QPC, we have realized a quantum ballistic transistor (voltage gain higher than 1), a new component useful for cryoelectronics thanks to its operating temperature and weak power consumption (about 1 nW). Moreover, the very low capacity of this component leads to promising performances for multiplexing low temperature bolometer dedicated to millimetric astronomy. The second study focused on HEMT with very high quality 2DEG. At 4. 2 K, a voltage gain higher than 20 can be obtained with a very low power dissipation of less than 100 μW. Under the above experimental conditions, an equivalent input voltage noise of 1. 2 nV/Hz^(1/2) at 1 kHz and 0. 12 nV/Hz^(1/2) at 100 kHz has been reached. According to the Hooge formula, these noise performances are get by increasing gate capacity estimated to 60 pF
15
Brown, Raphael. "A novel AlGaN/GaN based enhancement-mode high electron mobility transistor with sub-critical barrier thickness." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6590/.
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Power-switching devices require low on-state conduction losses, high-switching speed, high thermal stability, and high input impedance. Using gallium nitride (GaN) based field-effect transistors, these properties for switching devices can be satisfied. GaN-based High Electron Mobility Transistors (HEMTs) are emerging as promising candidates for high-temperature, high-power (power electronics) and radio-frequency (RF) electronics due to their unique capabilities of achieving higher current density, higher breakdown voltage, higher operating temperatures and higher cut-off frequencies compared to silicon (Si). Conventional GaN HEMTs with an aluminium gallium nitride (AlGaN) barrier are of depletion-mode (d-mode) or normally-on which require a negative polarity power supply to turn off. On the other hand, enhancement-mode (e-mode) or normally-off AlGaN/GaN HEMTs are attracting increasing interest in recent years because no negative gate voltage is necessary to turn off the devices. This leads to the advantage of simple circuit design and low stand-by power dissipation. For power electronics applications, power switches which incorporate e-mode devices provide the highly desirable essential fail-safe operation. In this research, a new high performance normally-off GaN-based metal-oxide-semiconductor (MOS) high electron mobility transistor (HEMT) that employs an ultrathin sub-critical 3nm Al_0.25Ga_0.75N barrier layer and relies on an induced two dimensional electron gas (2DEG) for operation was designed, fabricated and characterized. The device consists of source and drain Ohmic contacts nominally overlapped by the gate contact and employs a gate dielectric. With no or low gate-to-source voltage (V_GS), there is no two dimensional electron gas (2DEG) channel at the AlGaN/GaN interface to allow conduction of current between the drain and source contacts as the AlGaN barrier thickness is below the critical thickness required for the formation of such channel. However, if a large enough positive bias voltage V_GS is applied, it causes the formation of a quantum well at the AlGaN/GaN interface into which electrons from the source and drain Ohmic regions are attracted (by the positive gate voltage), effectively creating a 2DEG channel, and so the structure is a normally-off field effect transistor. Normally-off GaN MOS-HEMT devices were fabricated using plasma enhanced chemical vapour-deposited (PECVD) silicon dioxide (SiO_2) as the gate dielectric. They demonstrated positive threshold voltages (V_th) in the range of +1V to +3 V, and very high maximum drain currents (I_DSmax) in the range of 450mA/mm to 650mA/mm, at high gate voltage (V_GS) of around 6 V. The devices also exhibited breakdown voltages in the range of 9V and 17V depending on the gate dielectric thickness, making them suitable for realising high current low voltage power devices required, for instance, for buck converters for mobile phones, tablets, laptop chargers, etc.
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Park, Duke H. "Theoretical studies of submicron gate length high electron mobility transistors." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/13744.
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Su, Chih-Cheng, and 蘇志成. "Power High Electron Mobility Transistor with Buried Gate." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/94101168376702732540.
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碩士國立高雄大學
電機工程學系碩士班
94
Depletion-mode Al0.24Ga0.76As/In0.22Ga0.78As double heterojunction high electron mobility transistors (DH-HEMTs) were successfully fabricated with an as deposited gate to compare with those with a buried gate by annealing. Instead of a recessed gate, a buried gate used to control the distance between the gate and channel (and hence the aspect ratio) improves the series resistance. The measured transconductance of 150 mS/mm and an open-drain voltage gain of 136 for the DH-HEMT with an as deposited gate are enhanced to 175 mS/mm and 160 for the DH-HEMT with a 330-℃ annealing gate. Good device linearity is also obtained with very low second-harmonic to fundamental ratio of 3.55 %. The measured maximum fts (fmaxs) are 13.5, 13.5 and 14.5 (35, 37, and 37.5) GHz for DH-HEMTs with an as deposited, a 280-℃ and a 330-℃ annealing gates, respectively. Besides, the DH-HEMT with a 330-℃ annealing gate exhibits the highest PAE=44.8% and the lowest Fmin=1,46 dB at 2.4 GHz of all devices under the bias condition of the VDS = 3 V and VGS = �{1.0 V. Sinking gate metal into the Al0.24Ga0.76As Schottky barrier and hence changing the aspect ratio (Lg/deff, defined by the ratio of the gate length over the distance between the gate and channel) were employed in the simulation. The theoretical analysis and simulation are made by using a two-dimensional simulator Atlas. Based on the variations of the gate-metal sinking depth, the dc and rf performances are compared and studied
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Patnaik, Akash. "Breakdown Voltage Analysis of High Electron Mobility Transistor." Thesis, 2018. http://ethesis.nitrkl.ac.in/9646/1/2018_MT_216EE1273_APatnaik_Breakdown.pdf.
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Since the invention of the metal-oxide-semiconductor field-effect-transistor (MOSFET), the
semiconductor industry for electronics has been dominated by silicon (Si). The reason being the cost and ease of creating a native oxide on Si which enables the well established complementary metal-oxide-semiconductor (CMOS) process which has revolutionised the digital world we live in. Si, however,is a low band gap material (1.1 eV) and although used in power semiconductor sector over the years, new materials with superior properties are being investigated as potential replacements especially in power sector.Since past three decades, power management efficiency and cost have shown steady improvement as innovations in power MOSFET structures, technology, and circuit topologies have paced the
growing need for electrical power in our daily lives. In the last few years, however, the rate of improvement has slowed as the silicon power MOSFET has approached its theoretical bounds. Due to the limitations reached by silicon devices, new materials are emerging to cater the needs of today’s scenario. The prominent being the Gallium Nitride based High Electron Mobility Transistors.
GaN based devices have superior performance in field of power electronics as well as in many high frequency applications. This is due to its characteristic property of large bandgap,leading to high breakdown field and high mobility,allowing it to be used in high frequency applications. In the field of power converters two key power-switch requirements are there: (1) high blocking voltage with as small as possible resistance of the drift region that supports the blocking voltage and (2) high switching speed. Silicon based MOSFET have limitations of low breakdown voltage, high on resistance and low switching frequency. On contrary GaN based HEMT have high breakdown voltage capacity along with high switching speed which makes it far beyond its competitor, silicon based devices.
In this paper, breakdown voltage analysis is done and various aspects of improving the breakdown voltage are studied. On a specific note, detailed study on effect of passivation layer on breakdown voltage is done,considering structure miniaturisation, reduced on -resistance, high blocking voltage and high switching frequency. Moreover, passivation layer addition has multipurpose role in GaN based HEMT viz. removal of current collapse,protection to device, increment of breakdown voltage etc. Results from this study show electric field modification as the dielectric constant is increased. This modification is in terms of electric field distribution beneath gate-drain region especially at the drain edge of the gate. This lowering of electric field, as a result of distribution,helps in significant increment of breakdown voltage along with removal of current collapse. It is also observed that when pas sivation thickness is increased, breakdown voltage also increases.
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Chu, Fu Chuan, and 朱富權. "Development Of High-Performance GaN Based High Electron Mobility Transistor." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/19539485200728745953.
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博士長庚大學
電子工程學系
102
III-V nitride compound semiconductor based material system has been intensively studied over the past few decades. It has remarkable material properties not only for optoelectronics devices but also application in millimeter wave power devices. The nitride compound semiconductor material system has excellent properties such as wide direct band-gap, high electron mobility, high breakdown voltage, high operation frequency, excellent chemical and thermal stability, and chemically stable. These properties make GaN based materials very attractive for applications for AlGaN/GaN high electron mobility transistor (HEMT) devices. However, the large gate leakage current is the factor that most limits the direct current (DC) and radio frequency (RF) power performance of the conventional Schottky gate HEMTs. We interested in improving the HEMT device performance by deposited Er2O3 thin film for metal-oxide semiconductor high electron mobility transistor (MOS-HEMTs) fabrication. We suppress the gate leakage current and enhance microwave performance by Er2O3 thin film deposition for MOS-HEMTs. To reduce the gate leakage for conventional Schottky metal gate HEMTs, the high-K materials such as Pr2O, Hf2O3 and Al2O3 have been using as the gate dielectric to improve HEMT devices. However, by inserting an oxide layer between the gate metal and Schottky barrier layer leads to a threshold voltage shift owing to the series impedance of the oxide material and interface/fixed oxide charge. Thus, we use high-work-function metal oxide PdO for gate material to increase the Schottky barrier height to reduce gate leakage and improve device performance. We study a doping-free Gallium nitride (GaN) based High Electron Mobility Transistors (HEMTs) using AlN (300nm)/Al0.06GaN (0.7μm) composite buffer layers which were grown on 4H-SiC substrates by atmospheric pressure metal-organic chemical vapor deposition system (AP-MOCVD). The composite buffer HEMTs was developed and characterized. Finally, we propose the metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) by atomic-layer-deposited (ALD) deposited gallium oxide (Ga2O3) as the gate dielectric and surface passivation layer on AlGaN/AlN/GaN-SiC structure, that exhibited device performance superior to that of a conventional Schottky gate HEMT. Under similar bias conditions, the gate leakage currents of these MOS-HEMT devices were two orders of magnitude lower than those of conventional HEMTs, and meanwhile, the power-added -efficiency can be enhance up to 9%. The measured sub-threshold swing (SS) and the effective trap states density (Nt) of the MOS-HEMT were 78mV/decade and 3.621011cm–2, respectively. Improve devices performances of DC and RF property of the proposed MOS-HEMTs are comprehensibly investigated as compared with conventional HEMTs. In addition, the flicker noise characteristic is also observed to be lower in MOS-HEMTs than in conventional HEMT.
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Lai, Chenq-Hung, and 賴政弘. "The Application of TiO2 on High-Electron-Mobility Transistor." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/zn7ab6.
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碩士義守大學
電子工程學系
103
The study uses solution gelation (sol-gel) processed titanium dioxide (TiO2) as gate oxide layer of metal-oxide-semiconductor metamorphic high-electron-mobility transistor (MOS-MHEMT), the mixed solution was uniformly deposited on the surface of the InP Schottky layer using spin coating. The sol-gel method is simple compared with other oxide systems and this method need not involve excessive energy, the gate oxide using high permittivity may reduce the surface state and further improve the DC characteristics of device. For MOS-MHEMT using TiO2 as gate oxide layer, the saturated drain current density is 307 mA/mm which bias at the gate to source voltage of 2 V, and the peak transconductance is 193 mS/mm, the gate current density improved one order of magnitude, for the MOS-MHEMT, the turn on voltage is 7 V, and the breakdown voltage is -40 V.
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Li, Yi-Hsiu, and 李易修. "AlGaN/GaN High Electron Mobility Transistor for Sensor Application." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/13061740978817959467.
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碩士國立成功大學
光電科學與工程研究所
97
value of a solution under DC and AC biasing condition. For DC biasing condition, the channel resistance is found to decrease with reducing pH value under dark condition. The sensitivity is about 27.78 mV/pH when biasing the device with a constant current of 20 mA. The environmental lighting will induce parasitic effect to the measurement result. The channel resistance is observed to increase with reducing pH value of the solution when illuminated the device with a constant ultraviolet light. The effect of the ultraviolet illumination is also investigated. The pH value is also measured when biasing the device with AC current. Different types of AC signal from a pulse generator with different frequencies are injected into the devices and the signal is detected and analyzed by a lock-in amplifier. The sensitivity of the device is observed to depend on the type of AC signal and the frequency used. The maximum pH sensitivity is about 17 �嵢/pH when biasing with square waves with a frequency of 100 KHz. In conclusion, gateless HEMT chemical sensors are fabricated and analyzed. Both DC and AC biasing characteristics are studied. The ultraviolet illumination affects the device performance and should be controlled for future device application. A detailed understanding of the AC biasing condition will help to develop new sensor capability in the near future.
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林以寬. "Simulation for the high frequency high electron mobility transistor (HEMT) design." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/39145846952527677519.
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碩士逢甲大學
電子工程學系
102
We constructed the high electron mobility transistors by TCAD (Technology Computer Aided Design).The process of the mask design, deposited material and carrier concentration can be preciously confirmed to the actual process and effect. Moreover, the DC performances and the analyses of high-frequency small-signal signal were simulated in different respects. There are various HEMT models in this thesis. We observed that the gate voltage for double and single carrier supply layers devices might change the saturated current of channel. The saturated current was changed from 400 mA/mm to 36 mA/mm. The series resistances of source and drain would also affect the channel current. We also reduced the channel length and then investigated the high-frequency characteristics with the short-channel effects. And the cutoff frequency of short channel is 263.18 GHz. It is 24GHz higher than the cutoff frequency of long channel. Eventually, the effects on electrical properties caused by changing the ingredients of indium inside the channel were studied. The current gain is up to 46.46 dB and the power gain is 35.1 dB. The bandgap of capping material on both sides of channel with different lattice structure also were simulated to view the properties of the devices.. The TCAD combining complete physical theorems and mathematical formulas gives the whole pictures for the simulated devices. We can know the behaviors including the electron field of those devices by providing input signal quickly and precisely from block program in the TCAD. All qualities of those device were realized without fabricating a solid device.
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Hill, Adrian John. "An Analytic model for high electron mobility transistors." Thesis, 1986. http://hdl.handle.net/10413/6889.
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The last six years has seen the emergence and rapid development of a new
type of field effect transistor, the High Electron Mobility Transistor
(HEMT), which offers improved performance in both digital and analogue
circuits compared with circuits incorporating either MEtal Semiconductor
(MES) or Metal Oxide Semiconductor (MOS) FETs. A new physically-based
analytic model for HEMTs, which predicts the DC and RF electrical
performance from the material and structural parameters of the device,
is presented. The efficacy of the model is demonstrated with comparisons
between simulated and measured device characteristics, at DC and
microwave frequencies.
The good agreement with experiment obtained with the model indicates
that velocity overshoot effects are considerably less important in HEMTs
than has been widely assumed, and that the electron transit velocity in
submicron devices is approximately 10
cm/s, rather than around 2x10
cm/s.
The Inverted HEMT, one of the major HEMT structural variants, is
emphasized throughout this work because of its potential advantages over
other variants, and practical results from 0.5 micron gate length
Inverted HEMTs are presented.Thesis (Ph.D.)-University of Natal, Durban, 1986.
24
Lin, Yi-Feng, and 林義峯. "Fabrication and Study of AlGaN/GaN High Electron Mobility Transistor." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/26t232.
Full textAbstract:
碩士國立虎尾科技大學
光電與材料科技研究所
97
In recent years, the semiconductor fabrication was developed greatly. That is an important topic to get a high efficency device in the field of high frequency and high power device. Therefore, the researchs about devices were attended greatly by the research groups in the world. The high electron mobility transistor can get high electron mobility in the 2DEG, which located in the interface on AlGaN and GaN. In this thesis, first, we will introduce the properties, applications of GaN and the fundamental of HEMT. The HEMT structure was grew by metal-organic chemical vapor deposition system. The sheet carrier demsity and electron mobility of the sample were 1.36×10^13 cm^-2 and 1200 cm^2/V-sec in room temperature. We referred the fundamental of ohmic contact to use the circular transmission line model. We can get the lower specific contact resistance 5×10^-4 Ω-cm^2 from Ti/Al/Ni/Au(30/150/45/55nm), which was annealed in nitrogen ambience 825℃ 30sec. The SiO2 sidewall passivation can avoid the mesa etching induced the sidewall leakage and prevent the drop height of mesa lead the gate metal not continue. When the fabrication of the devices was finished, we will measure the direct current properties of variouse gate length sizes devices. We can get the maximum saturation current 349 mA/mm and maximum transconductance 94 mS/mm.
25
Shiau, Ying-Chern, and 蕭應辰. "Study of Double Heterojunction Power Pseudomorphic High Electron Mobility Transistor." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/83791465686251673278.
Full textAbstract:
碩士國立成功大學
電機工程學系
88
One way of improving the AlGaAs/GaAs conventional HEMT performance is to use InGaAs as the two-dimensional electron gas channel material instead of GaAs. Because the InGaAs pseudomorphic channel is buried inside the double heterojunction layers, the processing techniques developed for AlGaAs/GaAs conventional HEMTs can be used for pseudomorphic HEMTs without modification. Gate recess is a important process during the fabrication of PHEMT device. For power applications, a recess opening larger than the gate is necessary to obtain a large BVgd. Our investigations showed that a BVgd as high as 25V can be achieved by simply making a wide recess in the AlGaAs schottcy layer. The wide recess device exhibited a peak gm of 151mS/mm, and a maximum current density of 248mA/mm. The narrow recess device exhibited a lower gate to drain breakdown voltage of 8.7 volts, a peak gm of 173mS/mm, and a maximum current density of 267mA/mm. Based on all experimental results, we find that wide recess device shows good potential in high-power and high-frequency performance. At last, we have successfully demonstrate the air-bridge technique with electroplating process. The air bridge technique will provides us applications to realize interconnect for MMIC (Monolithic Microwave Integrated Circuits) and high power devices.
26
Hwu, Yuh-Feng, and 胡玉豐. "Study of GaAs/InGaAs/AlGaAs Pseudomorphic High Electron Mobility Transistor." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/66642656149149045039.
Full text
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WU, SHU-HSUAN, and 吳叔軒. "The simulation of GaAs High Electron Mobility Transistor using TCAD." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/43516714791861825712.
Full textAbstract:
碩士國防大學中正理工學院
電子工程研究所
97
Although silicon has been widely used in semiconductor foundry over a lot decades, the promising demands of microwave communications and wireless communications, with increasing importance in high-frequency communication products, have opened a new era for the compound semiconductor such as Gallium Arsenide. Nowadays, GaAs MESFET, GaAs HEMT and GaAs HBT all have been commercialized with specialized interests. Among them, GaAs HEMT with very high noise figure, could be widely used in the millimeter power amplifier, such as multi-stage low noise amplifiers and power amplifiers. Conventional HEMT such as AlGaAs/GaAs and pseudo-HEMT such as AlGaAs/InGaAs will be discussed in the paper. Describing the device topology and geometrical relationship first, and then the layer structure from the viewpoint of epilayer process will be discussed. The charge control analysis of layers relies on a self-consistent solution of Schrödinger’s and Poisson’s equations using Fermi-Dirac statistics and a 2-D density of states. Next, the small-signal equivalent circuit parameters and model parameters extraction method of intrinsic device and model parameters extraction method of extrinsic device are introduced, which will affect the transconductance and the cut-off frequency of the performance of HEMT. Eventually, the simulation results will be evaluated with the measured scattering parameters in determining the small-signal equivalent circuit
28
Yang, Chuang-Jeu, and 楊長舉. "Characteristics of pseudomorphic high electron mobility transistor under different temperature." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/24rf3f.
Full textAbstract:
碩士崑山科技大學
電機工程研究所
91
In this thesis, we use the In0.52Al0.48As Barrier layer to confine the electron in the In0.535Ga0.465As channel layer. The electon mobility can be improved by using InGaAs channel. The electron mobility are 9600 cm2/v-s and 37400 cm2/v-s under 300K and 77K, respectively. The characteristics of the device will be discussed under different temperature (300K, 325K, 350K, 375K, 400K, 425K). The extrinsic transconductance and saturatiom current density are 208mS/mm and 296mA/mm under 300K. The extrinsic transconductance and saturatiom current density are 166mS/mm and 268mA/mm under 77K. In the meanwhile, we simulate and measure the lattice quality of InGaAs channel layer by Double Crystal X-ray diffraction analyzer.
29
Huang, Jian-Jhang, and 黃建彰. "Effects of Passivation on AlGaAs/InGaAs High-Electron Mobility Transistor." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/59049183776568345749.
Full textAbstract:
碩士國立東華大學
光電工程研究所
97
In this thesis, AlGaAs/InGaAs/GaAs high-electron mobility transistors (HEMTs) grown by metalorganic chemical- vapor deposition(MOCVD) are porposed. The effects of hot-electron stress and sulfur passivation using (NH4)2Sx solution are studied. An interesting phenomenon after hot-electron stress is founded.Trapping and detrapping are induced by impact ionization when the hot electrons obtain the sufficient energy. However, gate current leakage is decreased. The sulfur passivation for AlGaAs materials on surface improves the surface smoothness, reduces the surface trapping, and enhances the DC and RF characteristics. The gate dimensions of HEMTs are 1.0 x 100 μm2. The HEMT with Au gate alloy has a maximum saturation drain current density of 363.5 mA/mm, a maximum extrinsic transconductance of 227.8 mS/mm and a gate-to-drain breakdown voltage of 7.9 V at 300 K. The HEMT with Au gate alloy and sulfur passivation has a maximum saturation drain current density of 493.5 mA/mm, a maximum extrinsic transconductance of 230.5 mS/mm and a gate-to-drain breakdown voltage of 10.9 V. Additionally, the RF performance, high frequency noise parameter and power characteristics are measured.The HEMT with sulfur passivation is more suitable for high speed, high power and low noise applications. There is a decaying phenomenon after hot-electron stress, but the breakdown voltage and gate current leakage of the devices are improved.
30
Wu, Tsung-Yeh, and 吳宗曄. "A Novel Dilute Antimony InGaAsSb Channel High Electron Mobility Transistor." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/08327497435796958237.
Full textAbstract:
碩士國立成功大學
微電子工程研究所碩博士班
94
This work reports, a high electron-mobility transistor (HEMT) using a dilute antimony In0.2Ga0.8As(Sb) channel, grown by the molecular beam epitaxy (MBE) system. The advantages by introducing the surfactant-like Sb atoms during growth of InGaAsN/GaAs quantum well (QW) consist of the suppression of the three-dimensional growth and the improved interfacial quality of the QW heterostructure. Besides, the present device exhibits better dc characteristics, highly stable thermal and frequency characteristics due to the improvement in the channel layer quality by using an In0.2Ga0.8As(Sb) channel. Distinguished device characteristics for GaAs/In0.2Ga0.8As(Sb) HEMT and conventional GaAs/In0.2Ga0.8As HEMT, with the gate dimensions of 1.2*200um2, include thermal threshold coefficient (¶Vth/¶T) is low to be -1.54 (-1.77) mV/K, gate-voltage swing (GVS) of 1.17 (1.15) V, peak extrinsic transconductance (gm, max) of 178 (166) mS/mm, and the current drive capability (IDSS) of 171 (157) mA/mm. The microwave characteristics for GaAs/In0.2Ga0.8As(Sb) HEMT and conventional GaAs/In0.2Ga0.8As HEMT, the unity gain cut-off frequency (fT) and the maximum oscillation frequency (fmax) are 25.6 (20.6) GHz and 28.3 (25.6) GHz, respectively.
31
Lin, Yi-Feng, and 林義? "Fabrication and Study of AlGaN/GaN High Electron Mobility Transistor." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/ch23ee.
Full textAbstract:
碩士國立虎尾科技大學
光電與材料科技研究所
97
In recent years, the semiconductor fabrication was developed greatly. That is an important topic to get a high efficency device in the field of high frequency and high power device. Therefore, the researchs about devices were attended greatly by the research groups in the world. The high electron mobility transistor can get high electron mobility in the 2DEG, which located in the interface on AlGaN and GaN. In this thesis, first, we will introduce the properties, applications of GaN and the fundamental of HEMT. The HEMT structure was grew by metal-organic chemical vapor deposition system. The sheet carrier demsity and electron mobility of the sample were 1.36×10^13 cm^-2 and 1200 cm^2/V-sec in room temperature. We referred the fundamental of ohmic contact to use the circular transmission line model. We can get the lower specific contact resistance 5×10^-4 Ω-cm^2 from Ti/Al/Ni/Au(30/150/45/55nm), which was annealed in nitrogen ambience 825℃ 30sec. The SiO2 sidewall passivation can avoid the mesa etching induced the sidewall leakage and prevent the drop height of mesa lead the gate metal not continue. When the fabrication of the devices was finished, we will measure the direct current properties of variouse gate length sizes devices. We can get the maximum saturation current 349 mA/mm and maximum transconductance 94 mS/mm.
32
Chen, Hsin-Hung, and 陳信宏. "Investigation of δ-doped InAlAs/InGaAs/InP High Electron Mobility Transistor." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/27107823135590119996.
Full textAbstract:
碩士逢甲大學
電子工程所
93
In this thesis, the characteristics of the InAlAs/InGaAs/InP HEMT with different channel structures by metal organic chemical vapor deposition (LP-MOCVD) have been studied. The channel structures were lattice-match channel, step-graded channel and inverse linear-graded channel, respectively. InP-based HEMTs have demonstrated excellent high frequency and low noise performance. But the power performance is limited by excessive leakage currents and relatively low breakdown voltage. In order to improve the breakdown characteristics, reduction of the channel thickness effectively leads to effectively suppression of impact ionization by limiting the electric field beneath the gate. Besides, we have grown an InP layer on the InAlAs Schottky layer, the etching stop layer, which is a viable solution to improve Vth reproducibility. It also contributes to suppressing kink effects in InP-based HEMTs and avoiding surface trap generation. From experimental results, Due to the intrinsic high-speed property of the high-In composition In0.56Ga0.44As subchannel design and the decreased separation distance between 2DEG and gate electrode, the SGC-HEMT exhibiting higher extrinsic transconductance, lower output conductance, higher voltage gain, and improved microwave performances, is suitable for high-frequency and high-gain millimeter-wave integrated circuit (MMIC) applications. On the other hand, ILGC-HEMT has demonstrated superior linearity, wider GVS regime, improved breakdown characteristics, improved current drive, and superior output power performance, due to the inverse linearly-graded InxGa1-xAs channel design. Consequently, the proposed ILGC-HEMT is suitable for high-power with good linearity MMIC applications. Besides, we also found using step-graded channel and inverse linear-graded channel structures in HEMTs can improve the thermal stability for its promising high-temperature applications.
33
Liang, Shih-Kai, and 梁仕楷. "Effect of Sulfur Treatment on AlGaAs/InGaAs High-Electron Mobility Transistor." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/e2aw24.
Full textAbstract:
碩士國立東華大學
材料科學與工程學系
95
In this thesis, we propose AlGaAs/InGaAs/GaAs high-electron mobility transistors (HEMTs) grown by metalorganic chemical- vapor deposition (MOCVD). The HEMTs with different gate alloys, including Au and Pt/Au. Moreover, using the (NH4)2x solution to from the AlGaAs surface passivation are studied and demonstrated. For AlGaAs material, the surface recombination velocity and surface states are reduced by sulfur passivation. Hence, the well-behaved interfaces between the epitaxial semiconductor and Schottky metals can be obtained. The gate dimensions of HEMTs are 1.0 x 100 μ㎡ gate. The HEMT with Pt/Au gate alloys and sulfur passivation has a maximum saturation drain current density of 329.4 mA/mm, a maximum extrinsic transconductance of 249 mS/mm and a gate-to-drain breakdown voltage of 25 V. The HEMT with Au gate alloys and sulfur passivation has a maximum saturation drain current density of 288 mA/mm, a maximum extrinsic transconductance of 200 mS/mm and a gate-to-drain breakdown voltage of 21.8 V. Additionally, the temperature-dependent behavior, microwave performance, high freauency noise parameter and power characteristics are measured. The improved performance shows that the studied HEMT with sulfur passivation layer has good potential for high speed and high power applications.
34
Lin, Yue-Min, and 林岳民. "Studies of Sb-contained Semiconductor Growth and High Electron Mobility Transistor." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/33091634512267619924.
Full textAbstract:
博士國立交通大學
電子工程學系 電子研究所
103
The purpose of this dissertation is to understand comprehensively the growth of the Sb-contained semiconductor material systems by MBE and the electronic characteristics of the type-I InAs/AlAsSb high electron mobility transistor on GaAs substrates. To suppress the formation of misfit and threading dislocations caused by the 8% lattice mismatch between the AlSb buffer layer and GaAs substrate, we have used two different methods. First, we developed a low defect buffer layer growth technique, which provides a high resistivity buffer with a smooth surface. This technique uses a periodically temperature-varying buffer layer composed of several pairs of thin AlSb layers. Through exploiting this method, an InAs-channel high electron mobility transistor on GaAs substrate was fabricated. Another method we have developed for high quality InAs quantum well channels is by improving the interfaces between the InAs channel and the Sb containing barrier layers. At antimonide/arsenide interfaces, it is possible to grow two different interfaces by molecular beam epitaxy because of the change of both the anion and cation between InAs and AlAsSb. One is an InSb-like interface and the other possibility is an AlAs-like interface. In this study, we found that the crystal quality of the InAs channel has a strong dependence on the type of the interface used. With the use of the InSb-like interface, the InAs quality is greatly improved. This is because the InAs lattice is aligned with the lattice of the buffer layer without any lattice relaxation. Compared with the AlAs-like type, the InAs lattice is relaxed and the crystal quality of the InAs channel is poor. The superior InAs quantum wells was demonstrated by showing high electron mobility and good surface morphology. Besides material improvement, we have also developed a new device structure, which had superior hole confinement in the presence of impact ionization. It results in much improved output characteristics for the devices. The new structure used in this study includes a type-I InAs/AlAsSb heterostructure. The FETs fabricated using this structure does not have the undesirable feedback effect from the holes generated by impact ionization. With the addition of the upper and lower AlAsSb barriers, impact-ionized holes are blocked from moving to the gate and buffer layer underneath and are confined in the channel. Thus, the gate current shows the regular leakage characteristic without any hump and the output I-V characteristics and the usable drain voltage range are greatly improved. To more clearly understand the growth behavior of III-V ternary compounds with different group-V elements like P, As and Sb, we did a detailed study on the incorporation of these elements during growth and its dependence on the strain and composition of the grown layer. We first study the growth of a GaAsSb layer on GaAs. We found that there is a naturally formed Sb gradient in the layer despite a fixed beam flux ratio. We also studied how the Sb distribution depends on the amount and type of strain in the grown layer. The strained GaAsSb layers on InP substrates were then grown. In this way, we investigated the incorporation of Sb with various strain conditions. We found the Sb distribution under tensile strain decreases as we move away from the interface and the Sb composition increases under compressive strain toward the surface. The work presented in this thesis not only gives us a better understanding on the growth of antimonide compounds but also provides a guideline for the growth of many important devices.
35
Wang, Ming-Zhan, and 王明展. "Characterization of Power Semiconductor Device: GaN High Electron Mobility Transistor (HEMT)." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/75689657125690554178.
Full textAbstract:
碩士健行科技大學
電子工程所
101
This research is make use of Stantaurus Workbench Integration of emiconductor device electrical and process simulation software to simulate GaN HEMT device electrical and analyze, Use GaN substrate grown on AlGaN as a barrier layer and then combining the GaN cap layer, and then to the SiN passivation treatment to complete the foundation structure of the HEMT, in this structure in a different dopant concentration, and the length of the metal electrode, electrical analysis Mohr fraction do. Discovery to the Gate and Drain spacing larger 2um, breakdown voltage relative increase nearly volts, and no obvious change in the case of changing the dopant concentration, contrary a slight deterioration of the signs, describes the this structure mainly affect the withstand voltage characteristics at the Gate and Drain spacing, The longer spacing relative higher the voltage resistance. last, in the research to identify Lsg = 2~3um, Lgd = 1~2um, the dopingdoping concentration range of 1x1014 ~1x1015 cm-3, the component breakdown voltage can be greater than 600V。
36
Kao, Chung-I., and 高忠義. "Fabrication of InGaAs/InAlAs/GaAs Metamorphic High Electron Mobility Transistor (MHEMT)." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/27271384219269892592.
Full textAbstract:
碩士國立成功大學
微電子工程研究所碩博士班
93
In this thesis, two InP-based heterostructure field-effect transistors (HFETs), grown by molecular beam epitaxy (MBE) system, have been fabricated and investigated. We evaporated platinum and gold as Schottky contact metals to obtain high-temperature performance. In addition, the highly selective succinic PH-adjusted solution is used to make recessed gate more precise and stable to increase device yield. For obtaining more power gain and bandwidth of transistors, we also fabricate sub-micron meter gate devices with resorting to deep ultraviolet (UV) photolithography. Experimentally, the devices show good DC, RF, and high-temperature characteristics. These advantages suggest that the studied devices are suitable for high-speed and high-power integrated circuit applications. First, we study InGaAs/InAlAs/GaAs metamorphic high electron mobility transistor. With high indium content in InGaAs channel layer, we obtain good transport property. Moreover, by employing the single d-doped sheet, it not only decreases the impurity scattering, but also increases the ability of carrier confinement. Second, we report InGaAs/InAlAs/GaAs metamorphic high electron mobility transistor with higher In mole fraction of InGaAs channel than that in first structure. Based on the use of double d-doped sheets, the current density and uniform distribution of carriers in channel layer are improved. Therefore, the device with wide drain current operation regime is obtained. In addition, due to the use of thicker Schottky layer, the gate leakage current can be decreased. Finally, the above structures are used to fabricate as sub-micron meter gate MHEMT. We discuss the differences between these two structures. Due to the reduction of gate length, both devices show good DC and microwave performances.
37
Tseng, Ching-Hsiang, and 曾靖翔. "InAlAs/InGaAs metamorphic high electron mobility transistor with InAlGaAs buffer layer." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/76389488991832422230.
Full textAbstract:
碩士國立成功大學
微電子工程研究所碩博士班
92
In this thesis, the characteristics of the In0.45Al0.55As/ In0.53Ga0.47As metamorphic high electron mobility transistors (MHEMT’s) with InAlGaAs buffer layer grown by Molecular beam epitaxy (MBE) have been studied. The InAlGaAs buffer layer in this structure not only accommodates the large lattice mismatch between the active layers and the GaAs substrate, but also replaces the InAlAs buffer layer as in the conventional design. The band gap of the InAlGaAs buffer layer is comparable or greater than the InAlAs band gap which resulted in good buffer layer isolation. We evaporated Au，Ni/Au，Ti/Au and Pt/Au as the Schottky contacts. The results show that different metal work function can get different Schottky barrier heights， the Schottky barrier heights increase can make the channel’s depletion region increase and enhance the pinch-off characteristics and the breakdown voltages obviously. The channel’s depletion region increases also can suppress impact ionization and kink effect，because the carriers in channel decrease. For a 1.2×100 μm2 gate dimension, the maximum saturation drain current density，extrinsic transconductance and breakdown voltage with different Schottky contacts have been described. The microwave，power and noise performances of the In0.45Al0.55As/ In0.53Ga0.47As metamorphic high electron mobility transistors have also been discussed. These good performances show that the studied structure with Pt/Au as the Schottky contact has good potential for high speed and amplification capability，and to realize the enhancement-mode device by making the Schottky contact thinner can be expected.
38
Chen, C. L., and 陳佳林. "Investigation of AlGaN/GaN High Electron Mobility Transistor on Si Substrate." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/13794608856334793374.
Full textAbstract:
碩士長庚大學
電子工程研究所
95
Si benefits high quality, being widely available as a large-diameter, low-cost substrate and extensive utilization in the semiconductor industry. In this thesis, High-electron-mobility transistors (HEMTs) based on the GaN two-dimensional electron systems (2DES) on Si substrates have been studied. In order to reduce the stress between the GaN and Si resulting from their lattice mismatch, AlN are used as an intermediate layer. The current density of GaN HEMT devices is coutributed by the 2DES formed by the GaN/AlGaN hetero-structures, originating from their spontaneous polarization and piezoelectric polarization. In this work, we inserted thin SiN layer to enhance the quality of the 2DES and improve a HEMT properties. In order to improve the HEMTs isolation characteristics, we utilize nitrogen ion-implantation for isolation. It can restrict the current flowing to the desired path (under the gate in HEMT) and electrically isolate separate device from each order. Characteristics of the epi-layers and devices were studied experimentally by XRD, transport properties, multifunctional mask, TLM (transfer length method), I-V, C-V and high frequency measurements. Comparisons of the saturated drain current density, trans- conductance, mobility, current gain cut off frequency (fT), power gain cut off frequency of operation (fMAX) between HEMTs on Si substrates with and without SiN treatment were made in this work. A same structure HEMT on sapphire substrate was also fabricated for reference. For AlGaN/GaN HEMT (with 5 um gate length and 65 um gate width).on Si substrate with SiN treatment, the mobility can be increased by more than 10 times, the maximum transconductance increased by 2~2.5 times, and the current gain cut off frequency (fT) increased more than 4 times at room temperature than the HEMTs on Si without SiN treatment. Details were discussed in this thesis.
39
Yeh, Jung-Po, and 葉榮博. "The Fabrication and Analysis of High-Power AlGaN/GaN High Electron Mobility Transistor." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/37874936774474346400.
Full textAbstract:
碩士國立臺灣大學
電子工程學研究所
102
GaN is a stable semiconductor material with wide bandgap of 3.4eV which can apply to high-voltage devices, and because of its direct-bandgap property, we commonly used in bright LED of short wavelength with 405nm. In addition,AlGaN/GaN hetero-junction has outstanding carrier transport property and high electron mobility because of the existence of two-dimensional electron gas with high concentration, and we can apply to high-power and high-frequency circuit operation. Currently, GaN is one of the most attractive semiconductor materials. Enhancement mode AlGaN/GaN MOSFETs fabricated by gate recessed technique and MIS structure is mentioned in this study. Reactive ion etching using a high-density systems (HDP-RIE) dry etch the gate recessed area with BCl3/Cl2/Ar gas can effective improve the etching selectivity ratio and reduce surface roughness. Hope to reduce the element of damage. Furthermore, the gate dielectric material grew by ALD (Atomic Layer Deposited) with high k such as aluminum oxide, hafnium oxide can reduce the gate leakage and enhance the current density. In this thesis,we research gate-last fabrication process and discuss metal-gate/high-κ dielectric stacks in the annealing process feasibility,We analyze the results, and hope that the process can be used to GaN fabrication in the future.
40
Lee, Chien-Chyi, and 李建騏. "Fabrication of High Electron Mobility Transistors." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/24033735449938189380.
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Hsieh, Yu-Lung, and 謝裕隆. "Camel-Gate High-Electron Mobility Transistors." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/42978268891684071284.
Full textAbstract:
碩士國立東華大學
材料科學與工程學系
93
Abstract In this thesis, we propose InAlGaP/InGaAs camel-gate high-electron mobility transistors (CAM-HEMTs) grown by metalorganic chemical- vapor deposition (MOCVD). InAlGaP/GaAs HEMTs have the reduced gate current and increased breakdown because InAlGaP/GaAs has the large conduction-band discontinuity and InAlGaP has large bandgap. For comparison, the CAM-HEMTs with different gate metals, including Pt/Au, Au, Ti/Au, and Ti/Au, are studied. The CAM-HEMT with Ni/Au gate metal exhibits the high barrier height, low leakage current, and high two- and three-terminal breakdown voltages. Finally, the temperature-dependent maximum drain current, extrinsic transconductance and breakdown voltage of the CAM-HEMTs are also investigated. Experimental results demonstrate that the CAM-HEMTs developed herein are appropriate for high power applications.
42
Huang, Chong Rong, and 黃崇榕. "High RF Performance AlGaN/GaN High Electron Mobility Transistor with AlGaN Back Barrier Design." Thesis, 2019. http://ndltd.ncl.edu.tw/cgi-bin/gs32/gsweb.cgi/login?o=dnclcdr&s=id=%22107CGU05124003%22.&searchmode=basic.
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Hung, Sheng-Chun, and 洪聖均. "Gas and Liquid Sensors based on AlGaN/GaN High Electron Mobility Transistor." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/98701702288735669832.
Full textAbstract:
博士國立中央大學
物理研究所
98
In this thesis, we study gas and liquid sensors based on AlGaN/GaN high electron mobility transistor. For gas sensor, AlGaN/GaN high electron mobility transistors (HEMTs) with a polarized polyvinylidene difluoride (PVDF) film coated on the gate area exhibited significant changes in channel conductance upon exposure to different ambient pressures. The PVDF thin film was deposited on the gate region with an ink-jet plotter. Next, the PVDF film was polarized with an electrode located 2 mm above the PVDF film at a bias voltage of 10kV and 70℃. Variations in ambient pressure induced changes in the charge in the polarized PVDF, leading to a change in surface charges on the gate region of the HEMT. Changes in the gate charge were amplified through the modulation of the drain current in the HEMT. By reversing the polarity of the polarity of the polarized PVDF film, the drain current dependence on the pressure could be reversed. The limit of detection of our gas pressure device was 1 psig (51.7 mmHg) using a 20 × 50 µm2 gate sensing area. For liquid sensor, AlGaN/GaN HEMTs with an Ag/AgCl gate exhibit significant changes in channel conductance upon exposing the gate region to various concentrations of chloride (Cl-) ion. The Ag/AgCl gate electrode, prepared by potentiostatic anodization, changes electrical potential when it encounters Cl- ions. This gate potential changes lead to a change of surface charge in the gate region of the HEMT, inducing a higher positive charge on the AlGaN surface, and increasing the piezoinduced charge density in the HEMT channel. These anions create an image positive charge on the Ag gate metal for the required neutrality, thus increasing the drain current of the HEMTs. The HEMTs source-drain current was highly dependent on Cl- ion concentration. The limit of detection of our device achieved was 1×〖10〗^(-8)M using a 20 × 50 µm2 gate sensing area.
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Yang, Ya-wen, and 楊雅雯. "Enhancement-mode Pseudomorphic High Electron Mobility Transistor Model and Microwave Power Amplifier." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/98383367635348155630.
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碩士國立中央大學
電機工程研究所
97
Power amplifier is a very important component in the wireless transmitter. The high performance power amplifier must depend on accurate nonlinear device model. In this thesis, an accurate nonlinear model and a high linearity power amplifier are designed, analyzed, and demonstrated for InGaAs pHEMT. We proposed a novel current model for 0.5 μm InGaAs pHEMTs enhancement-mode device. The model is differentiable for any order at full bias range by utilizing smooth function technique in the symbolical defined device environment (SDD). The Statz charge model is included for device capacitance in this model. The proposed model predicted the DC, S-parameters, microwave power, and nonlinear distortion characteristics more accurate in comparison with conventional compact model. Further, the model is convenient and direct to be embedded in commercial harmonic balanced simulator. Utilizing nonlinear model tools, the high performance power amplifier was realized for WiMAX applications. The predistortion method in this work was used to improve AM-AM and AM-PM distortion at high power operation without degrading the intrinsic performance. The power amplifier was successfully demonstrated at 3.5 GHz. The power performances were power gain of 16 dB, maximum power of 29.5 dBm, output linear power (P1dB) of 27.5 dBm. The measured EVM was smaller than 3.5 % using 3.5 GHz 64 QAM WiMAX signal.
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Chin, Yin-Shuan, and 金胤軒. "Fabrication and Characterization of AlGaN/GaN High Electron Mobility Field Effect Transistor." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/88935188858030454642.
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Singh, Vikash Kumar. "Next Generation High Electron Mobility Transistor based on InGaN Quantum Well Channel." Thesis, 2019. https://etd.iisc.ac.in/handle/2005/4591.
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In past two decades and more, III-N based high electron mobility transistors (HEMTs) have generally used GaN as the channel layer. During this period, the quest for operating it at higher frequencies has resulted in the evolution of different heterostructures viz. Ga-polar AlGaN/GaN, AlGaN/AlN/GaN, InAlN/AlN/GaN, InAlGaN/AlN/GaN etc. as well as its N-polar variants. As a result of technological developments related to epitaxial growth and device processing, the performance of such HEMTs have shown significant progress in recent years and are approaching their performance limits. Such high frequency devices are the key components of many communication systems, defence systems and sensors operating at mm- and sub-mm wave frequencies. To meet such requirements, the operating frequencies can be increased even more by addressing the intrinsic delay (τ=Lgate/vsat) via increase in the electron velocity (vsat). In this context, InGaN is a promising material for the channel layer due to an increase in electron saturation velocity with InN fraction.
As part of the present work, theoretical and experimental aspects required for the development of InxGa1-xN QW channel HEMTs with 0
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Eliza, Sazia Afreen. "Modeling of AlGaN/GaN High Electron Mobility Transistor for Sensors and High-Temperature Circuit Applications." 2008. http://trace.tennessee.edu/utk_graddiss/514.
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With the most advanced and mature technology for electronic devices, silicon (Si) based devices can be processed with practically no material defects. However, Si technology has difficulty meeting the demand for some high-power, high-speed, and high-temperature applications due to limitations in its intrinsic properties. Wide bandgap semiconductors have greater prospects compared to Si based devices. The wide band gap material system shows higher breakdown voltage, lower leakage, higher saturation velocity, larger thermal conductivity and better thermal stability suitable for high-power, high-speed, and high-temperature operations of the devices. In recent years, GaN based devices have drawn much research attention due to their superior performances compared to other wide bandgap semiconductor (SiC) devices. Specifically, implementation of AlGaN/GaN high electron mobility transistor (HEMT) based power amplifiers have become very promising for applications in base stations or radar. With the increase in device power, channel temperature rises. This introduces high-temperature effects in the device characteristics. In addition, high-power, high-frequency and high-temperature operation of AlGaN/GaN HEMT is required for telemetry in extreme environment.
AlGaN/GaN HEMT also shows great potential as chemically selective field-effect transistor (CHEMFET). Due to simpler imprint technique and amplification advantages CHEMFET based detection and characterization of bio-molecules has become very popular. AlGaN/GaN HEMT has high mobility two-dimensional electron gas (2 DEG) at the hetero-interface closer to the surface and hence it shows high sensitivity to any surface charge conditions.
The primary objective of this research is to develop a temperature dependent physics based model of AlGaN/GaN HEMT to predict the performance for high-power and high- speed applications at varying temperatures. The physics based model has also been applied to predict the characteristics of AlGaN/GaN HEMT based CHEMFET for the characterization of bio-molecular solar batteries - Photosystem I reaction centers. Using the CHEMFET model, the number of reaction centers with effective orientation on the gate surface of the HEMT can be estimated.
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Wu, Wen Hsin, and 吳文信. "Design and Characteristic of AlGaN/GaN High-Electron-Mobility-Transistor with Nanoribbons Structure." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/hdw99w.
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Huang, Yu-Chian, and 黃宇謙. "InGaP and AlGaAs Metal-Oxide-Semiconductor High-Electron-Mobility Transistor on Si substrate." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/5tujhp.
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碩士義守大學
電子工程學系
105
Native oxide as gate insulators on InGaP and AlGaAs high electron mobility transistors (HEMT) were fabricated and characterized in this thesis through a liquid phase oxidation (LPO) method. Compared with others, the method is a simple, economic, and effective technique used to form a native oxide layer on GaAs material at near-room temperature (30-70°C). For the InGaP MOS-HEMT DC characteristics, the maximum drain current density is 203.4 mA/mm, the maximum peak transconductance is 128.5 mS/mm at the VDS = 2 V, two-terminal diode of the reverse breakdown voltage is -13 V for MOS-HEMT. For the AlGaAs MOS-HEMT DC characteristics, the maximum drain current density is 149.3 mA/mm, the maximum peak transconductance is 100.6 mS/mm at the VDS = 2 V, two-terminal diode of the reverse breakdown voltage is -38.5 V for MOS-HEMT. For the InGaP Microwave characteristics , the cut-off frequencies of conventional HEMT and MOS-HEMT are 4.5 GHz and 5.9 GHz; the maximum oscillation frequencies are 4.6 GHz and 8.4 GHz, respectively. For the AlGaAs Microwave characteristics , the cut-off frequencies of conventional HEMT and MOS-HEMT are 3.8 GHz and 5.7 GHz; the maximum oscillation frequencies are 3.9 GHz and 6.3 GHz, respectively. The low frequency noises are improved significantly. Consequently, the InGaP and AlGaAs MOS-HEMT with liquid phase oxidized GaAs as gate insulator is promising for low noise and high speed applications.
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CHU, LI HSIN, and 褚立新. "The study of Enhancement-mode InGaP/AlGaAs/InGaAs Pseudomorphic High Electron Mobility Transistor." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/52835255368169983220.
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博士國立交通大學
材料科學與工程系所
96
In recent years, digital wireless communication technology develops rapidly around the world. It is believed that the digital wireless technologies are the major trends for the future wireless communication systems. The purpose of this dissertation is to develop the Enhancement-mode high-electron-mobility transistor (HEMT) for the digital wireless communication systems with improved device structures and the related process technologies. In this dissertation, the InGaP/AlGaAs/InGaAs structure was used to fabricate the enhancement-mode high-electron-mobility transistors with the goal of further enhancement of the HEMT device performance. The attempt on using the InGaP/AlGaAs/InGaAs heterojunction instead of the InGaP/InGaAs is due to: Firstly, the conduction band discontinuity of the AlGaAs/InGaAs interface is superior to those form at the InGaP/InGaAs interface, the carrier confinement would be better. This will improve the output power performance of the InGaP PHEMTs. Secondly, the interface between the AlGaAs/InGaAs interface is smoother than the InGaP/InGaAs interface due to the interdiffusion behavior of As and P atoms in the InGaP/InGaAs interface. As a result, the electron mobility of the InGaP/AlGaAs/InGaAs PHEMTs is higher than the electron mobility of the InGaP/InGaAs PHEMTs. The fabricated InGaP/AlGaAs/InGaAs HEMT 0.5×160 μm2 device shows low knee voltage of 0.3V, a high drain-source current (IDS) of 375mA/mm and a maximum transconductance of 550mS/mm when drain-source voltage (VDS) was bias at 2.5V. High-frequency performance was also evaluated; the cut-off frequency (Ft) was 60GHz and the maximum oscillation frequency (Fmax) was 128GHz. The E-mode InGaP/AlGaAs/InGaAs PHEMT also exhibited high output power density of 453mW/mm with high linear gain of 30.5dB at 2.4GHz. The maximum power-added-efficiency (PAE) of the device was 70%, when tuned for the maximum power added efficiency. On the other hand, advanced digital wireless application systems, such as Wide-band Code-Division Multiple-Access (W-CDMA) system, has imposed stringent requirements on the devices while include high efficiency and high linearity operation with minimum DC power consumption. Thus, a high linearity and high efficiency Enhancement-mode InGaP/AlGaAs/InGaAs PHEMT has to be developed. The low voltage operation is achieved by the very low knee voltage of the device and the linearity is improved by optimizing the concentrations of the two delta-doped layers. Biased at a drain-to-source voltage VDS = 2V, the fabricated device exhibited a maximum transconductance of 448 mS/mm. The measured minimum noise figure (NFmin) was 0.86 dB with 12.21 dB associated gain at 10 GHz. The device shows a high output third order intercept point (OIP3)-P1dB of 13.2 dB and a high power efficiency of 35% when under wideband code-division multiple-access (W-CDMA) modulation signal. In addition, an Enhancement-mode InGaP/AlGaAs/InGaAs PHEMT using Platinum (Pt) as the Schottky contact metal was investigated for the first time. Following the Pt/Ti/Pt/Au gate metal deposition, the devices were thermally annealed at 325℃ for gate sinking. After the annealing, the device showed a positive threshold voltage (Vth) shift from 0.17V to 0.41V, and a very low drain leakage current of 0.16μA/mm which was reduced from 1.56μA/mm before gate sinking. These improvements are attributed to the Schottky barrier height increase and the decrease of the gate to channel distance as Pt sink into the InGaP Schottky layer during gate sinking process. The shift in the Vth was very uniform across a four inch wafer and was reproducible from wafer to wafer. The device also showed excellent RF power performance after the gate sinking process. Finally, we had investigated the interfacial reaction between platinum and InGaP in a Schottky diode structure. There was a 7.5 nm-thick amorphous layer formed at the interface between Pt and InGaP after metal deposition. After annealing at 325 ℃ for one minute, this amorphous layer increased to 12.8 nm and the reverse leakage current also decreased. The diffusion of Pt atoms and crystallization of amorphous layer took place after annealing at 325℃ for 10 minutes. Prolonging the annealing to 3 hours led to formation of Ga2Pt and GaPt3 phases in InGaP and Schottky diodes degraded after these new phases were observed.