Fundamental investigation of high temperature operation of field effect transistor devices

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Title Fundamental investigation of high temperature operation of field effect transistor devices
Publication Type dissertation
School or College College of Engineering
Department Materials Science & Engineering
Author Chern, Jehn-Huar
Date 2011-12
Description In this dissertation copper germanium (CuGe)-based materials were investigated as potential ohmic contacts to n-type gallium arsenide (GaAs). The CuGe-based contacts to GaAs were found to not form any reaction products with GaAs and to have low contact resistance comparable to that of nickel gold germanium (NiAuGe) ohmic contacts to GaAs. The potential for high temperature applications using CuGe ohmic contacts was investigated. A guideline for further reduction of the contact resistance has been achieved after investigating the detailed mechanism of the formation of binary CuGe contacts over a wide range of Ge concentrations. The thermal stability of CuGe contacts was significantly enhanced and improved by introducing a diffusion barrier, titanium tungsten nitride (TiWNx), and a gold (Au) overlayer for high temperature applications. Novel approaches such as epitaxial thulium phosphide (TmP) Schottky contacts and the utilization of low temperature (LT)-aluminum gallium arsenide (AlGaAs) were also investigated in this dissertation and likely will be the standard technologies for a new generation of high-temperature electronics. Inserting a layer of aluminum arsenide (AlAs) underneath the channel of a GaAs-based MESFET was found to reduce substrate leakage currents by a factor of 30 compared with the same MESFET directly fabricated on a semi-insulating GaAs substrate. In addition to AlAs, and AlxGa1-xAs materials, new materials grown at low temperatures such as LT-AlGaAs were used in heterojunction FET structures as a back wall barrier. Low drain leakage currents were achieved using AlAs and LT-AlGaAs as the back wall barriers. Some fundamental properties regarding these materials are of great interest and in need of further characterization. Part of the work in this dissertation was devoted to the characterization of device performance for different structure designs at elevated temperatures. The suitability of GaAs-based and gallium arsenide (GaN)-based MESFET, JFET, pseudomorphic-HEMT, and modulation doped FET (MODFET) devices for high-temperature applications were investigated and addressed in terms of device performance such as transconductance, leakage current density, and current gain. Wide gap materials such as GaN have low carrier generation rate at high temperatures and, hence, high operation temperature capabilities and potential.
Type Text
Publisher University of Utah
Subject Contact thermal stability; Cu3Ge TiWN LT AlGaAs TmP; Field effect transistor device; GaN MODFET; High temperature operation; Ohmic Schottky contacts GaAs AlGaAs GaN
Dissertation Institution University of Utah
Dissertation Name Doctor of Philosophy
Language eng
Rights Management Copyright © Jehn-Huar Chern 2011
Format application/pdf
Format Medium application/pdf
Format Extent 7,182,322 bytes
Identifier us-etd3,72546
Source Original housed in Marriott Library Special Collections, TK7.5 2011 .C44
ARK ark:/87278/s69g62jd
Setname ir_etd
ID 194611
Reference URL https://collections.lib.utah.edu/ark:/87278/s69g62jd
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