Gate recess engineering of pseudomorphic In0.30GaAs/GaAs HEMTs

The authors report how the performance of 0.12 μm GaAs pHEMTs is improved by controlling both the gate recess width, using selective dry etching, and the gate position in the source drain gap, using electron beam lithography. pHEMTs with a transconductance of 600 mS/mm, off state breakdown voltages >2 V, fτ of 120 GHz, f max of 180 GHz and MAG of 13.5 dB at 60 GHz are reported

Physics of InAIAs/InGaAs Heterostructure Field-Effect Transistors

Contains an introduction, a report on one research project and a list of publications and conference papers.Joint Services Electronics Program Contract DAAH04-95-1-0038Texas Instrument

Effects of deep levels on transconductance dispersion in AlGaAs/InGaAs pseudomorphic high electron mobility transistor

The effects of deep levels on the transconductance dispersion in an AlGaAs/InGaAs pseudomorphic high electron mobility transistor was interpreted using capacitance deep level transient spectroscopy (DLTS). Transconductance was decreased by 10% in the frequency range of 10 Hz-10 kHz at the negative gate bias, but it was increased at the positive one. In the DLTS spectra, two hole trap-like signals corresponding to surface states were only observed at the negative pulse bias, whereas the DX-center with the activation energy of 0.42 +/- 0.01 eV were observed at the positive one. The activation energy agrees well with that obtained from the temperature dependence of the positive transconductance dispersion, 0.39 +/- 0.03 eV. These provide evidence that the positive and negative transconductance dispersions are due to the DX center and surface states, respectively.open9

Smart Power Devices and ICs Using GaAs and Wide and Extreme Bandgap Semiconductors

We evaluate and compare the performance and potential of GaAs and of wide and extreme bandgap semiconductors (SiC, GaN, Ga2O3, diamond), relative to silicon, for power electronics applications. We examine their device structures and associated materials/process technologies and selectively review the recent experimental demonstrations of high voltage power devices and IC structures of these semiconductors. We discuss the technical obstacles that still need to be addressed and overcome before large-scale commercialization commences

Electrical degradation mechanisms of RF power GaAs PHEMTs

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Vita.Includes bibliographical references (p. 155-161).GaAs Pseudomorphic High-Electron Mobility Transistors (PHEMTs) are widely used in RF power applications. Since these devices typically operate at high power levels and under high voltage biasing, their electrical reliability is of serious concern. Previous studies have identified several distinct degradation phenomena in these devices, but a complete picture has yet to be formed. In this study, we have carried out a comprehensive study of the mechanisms of electrical degradation on a set of experimental RF power GaAs PHEMTs (non-commercial devices provided by our sponsor, Mitsubishi Electric). A wide variety of electrical stressing experiments employing different conditions (varying temperature, bias, environment) were performed on these devices in order to monitor their degradation with stressing. Our general observations showed several forms of degradation, the most concerning being an increase in the drain resistance RD and a reduction in maximum drain current Imax. Contrary to what is often claimed in the literature, our experiments indicated that these forms of degradation were not driven by impact-ionization or hot-electron effects. Instead, we found the degradation to be strongly correlated with temperature, stressing environment, and drain-gate bias, which were all consistent with a corrosion mechanism. Via materials analysis we were able to confirm that the degradation of both RD and Imax were due to surface corrosion on the drain side of the device, albeit at different specific locations. The increase in RD was attributed to oxidation on the n+GaAs ledge, while the reduction in Imax was due to oxidation on the AlGaAs surface, closer to the gate.(cont.) A recoverable negative shift in the threshold voltage VT and a permanent decrease in Rs were also observed during electrical stressing. The shift in VT was attributed to field-assisted tunneling of electrons out of traps under the gate, while the decrease in Rs was found to be consistent with recombination-induced annealing of defects on the source side of the device. Measurements were also performed to observe light emitted from the device during electrical stressing. The observed light-emission indicated that device degradation was proceeding in a highly non-uniform manner across the width of the device, due to a non-uniform electric field distribution. We attributed this to a non-uniform recess geometry across the device width. This suggested that it is important to ensure uniform geometry across the device width, in order to minimize non-uniformities in electric field distribution and enhance device reliability. The physical understanding developed in this work should be instrumental to identifying and addressing future reliability issues in RF power GaAs PHEMTs.by Anita Villanueva.Ph.D

Surface states on n-type Al0.24Ga0.76As characterized by deep-level transient spectroscopy

Capacitance deep-level transient spectroscopy (DLTS) was used to study surface states on aluminum compounds. Two hole-like traps were observed in pseudomorphic high-electron-mobility transistor with a multifinger gate. No hole-like signals were observed in the DLTS spectra of the fat field-effect transistor (FATFET) having negligible ratio of the ungated surface to the total area between the source and the drain. The activation energies of both surface states were measured to be 0.50??0.03 and 0.81??0.01 eV.open6

Power limiting mechanisms in InP HEMTs

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (leaves 57-59).by Christopher S. Putnam.M.Eng