@article{bilbro_trew_2015, title={A Five-Parameter Model of the AlGaN/GaN HFET}, volume={62}, ISSN={["1557-9646"]}, DOI={10.1109/ted.2015.2394376}, abstractNote={We introduce an analytic expression for the drain current Id(Vgs, Vds) of an AlGaN/GaN heterojunction field-effect transistor (HFET) as a function of its gate and drain voltages. We derive the function from a compact physical model of conduction current in the HFET. The proposed expression for the current is configured by five parameters, which can be expressed in terms of the geometry and materials of a device. We extend the model to small-signal RF operation by embedding it in a 12-parameter RLC network that represents terminal feed impedances and device parasitics. We adjust the parameters of the extended model to simultaneously fit dc and RF measurements of an industrial transistor.}, number={4}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Bilbro, Griff L. and Trew, Robert J.}, year={2015}, month={Apr}, pages={1157–1162} }
 @article{goswami_trew_bilbro_2014, title={Modeling of the Gate Leakage Current in AlGaN/GaN HFETs}, volume={61}, ISSN={["1557-9646"]}, DOI={10.1109/ted.2014.2302797}, abstractNote={A new physics-based model of the gate leakage current in AlGaN/GaN heterojunction field effect transistors (HFETs) is demonstrated. The model predicts accurately the gate-leakage current for a wide range of gate-drain voltage. The model is based on the formulation of tunneling and space charge limited (SCL) current flow. The gate leakage current is shown to flow through two paths: 1) the surface of the device establishes the primary path and the current transport mechanism is modeled using SCL transport in the presence of shallow traps and 2) the traps in the AlGaN layer assist in the tunneling of electrons from the gate to the 2-D electron gas, which flows to the drain electrode constituting the second path for the leakage current. The trap levels extracted from the model are consistent with the reports presented in the literature. The model appropriately explains the gate leakage current of the AlGaN/GaN HFETs for drain voltages up to 170 V and is verified by comparing the model results with the measured gate leakage data of industrial devices.}, number={4}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Goswami, Arunesh and Trew, Robert J. and Bilbro, Griff L.}, year={2014}, month={Apr}, pages={1014–1021} }
 @article{goswami_trew_bilbro_2014, title={Physics of gate leakage current in N-polar InAlN/GaN heterojunction field effect transistors}, volume={116}, ISSN={["1089-7550"]}, DOI={10.1063/1.4900581}, abstractNote={A physics based model of the gate leakage current in N-polar InAlN/GaN heterojunction field effect transistors is demonstrated. The model is based on the space charge limited current flow dominated by the effects of deep traps in the InAlN surface layer. The model predicts accurately the gate-leakage measurement data of the N-polar InAlN/GaN device with InAlN cap layer. In the pinch-off state, the gate leakage current conduction through the surface of the device in the drain access region dominates the current flow through the two dimensional electron gas channel. One deep trap level and two levels of shallow traps are extracted by fitting the model results with measurement data.}, number={16}, journal={JOURNAL OF APPLIED PHYSICS}, author={Goswami, Arunesh and Trew, Robert J. and Bilbro, Griff L.}, year={2014}, month={Oct} }
 @article{hou_bilbro_trew_2013, title={A Compact Physical AlGaN/GaN HFET Model}, volume={60}, ISSN={["1557-9646"]}, DOI={10.1109/ted.2012.2227323}, abstractNote={We introduce a physics-based compact model for AlGaN/GaN heterojunction field-effect transistors (HFETs) that is suitable for both RF microwave and switched-mode power supply (SMPS) applications, so that RF techniques can help determine HFET performance in SMPS applications. Such simulations can predict the on-resistance, slew rate, and breakdown voltage from the physical design of the transistor. Starting from an expression for the drain-source conduction current, charge distribution and displacement current are determined. The new model was implemented in Verilog-A and implemented in AWRDE, the design environment from Applied Wave Research. The HFET model was validated by comparison with Silvaco simulations and with data from an AlGaN/GaN HFET S-band amplifier. The new model accurately predicts device performance for dc, small-signal, and large-signal operations.}, number={2}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Hou, Danqiong and Bilbro, Griff L. and Trew, Robert J.}, year={2013}, month={Feb}, pages={639–645} }
 @article{goswami_trew_bilbro_2013, title={Physics based modeling of gate leakage current due to traps in AlGaN/GaN HFETs}, volume={80}, ISSN={["1879-2405"]}, DOI={10.1016/j.sse.2012.10.005}, abstractNote={Abstract A new model for the gate leakage current in AlGaN/GaN HFETs is demonstrated. The model is completely physical and is based on the formulation of space charge limited current flow. Two levels of shallow traps in the AlGaN surface layer are considered to evaluate the model. The depth of the traps is consistent with the reports presented in the literature. The model adequately explains the measured gate leakage current and for the first time, predicts accurately the experimentally observed change in slope of the gate leakage current versus the gate to drain voltage.}, journal={SOLID-STATE ELECTRONICS}, author={Goswami, A. and Trew, R. J. and Bilbro, G. L.}, year={2013}, month={Feb}, pages={23–27} }
 @article{kong_trew_kim_2013, title={Toward stimulated interaction of surface phonon polaritons}, volume={114}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.4851717}, DOI={10.1063/1.4851717}, abstractNote={Thermal emission spectra mediated by surface phonon polariton are examined by using a theoretical model that accounts for generation processes. Specifically, the acoustic phonon fusion mechanism is introduced to remedy theoretical deficiencies of the near thermal equilibrium treatments. The model clarifies the thermal excitation mechanism of surface phonon polaritons and the energy transfer path under non-zero energy flow. When applied to GaAs and SiC semi-infinite surfaces, the nonequilibrium model predicts that the temperature dependence of the quasi-monochromatic peak can exhibit distinctly different characteristics of either sharp increase or slow saturation depending on the materials, which is in direct contrast with the estimate made by the near-equilibrium model. The proposed theoretical tool can accurately analyze the nonequilibrium steady states, potentially paving a pathway to demonstrate stimulated interaction/emission of thermally excited surface phonon polaritons.}, number={23}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Kong, B. D. and Trew, R. J. and Kim, K. W.}, year={2013}, month={Dec}, pages={233508} }
 @article{schimizzi_trew_bilbro_2012, title={A Simplified Physical Model of RF Channel Breakdown in AlGaN/GaN HFETs}, volume={59}, ISSN={["1557-9646"]}, DOI={10.1109/ted.2012.2211360}, abstractNote={A temperature-dependent impact-ionization-initiated RF breakdown model in the 2DEG channel of AlGaN/GaN HFETs is reported. When operating these devices in RF power amplifier circuits, impact ionization in the channel has a significant effect upon gain saturation, power-added efficiency, and output power. An analytical physics-based model of channel breakdown is formulated based on TCAD investigations of the internal device behavior. This model is integrated with an existing physics-based HFET compact model and accurately predicts large-signal device performance. Values of thermal resistance and the breakdown temperature coefficient were extracted from simulations of an industrial HFET and are in agreement with the literature, thus validating that the model captures the dominant breakdown mechanism.}, number={11}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Schimizzi, Ryan D. and Trew, Robert J. and Bilbro, Griff L.}, year={2012}, month={Nov}, pages={2973–2978} }
 @inproceedings{trew_hou_schimizzi_goswami_bilbro_2012, title={Large-signal FET Models and a New AlGaN/GaN HFET model for power amplifier design}, DOI={10.1109/icwits.2012.6417696}, abstractNote={A historical review of large-signal compact FET models is presented. Device models used in circuit design typically are based upon equivalent circuit techniques. However, it is possible to develop physics-based compact models. In this work, a new physics-based model for AlGaN/GaN HFETs that can be integrated into the commercial simulators is described. The new model has demonstrated good agreement between measured and simulated data for communications band power amplifiers.}, booktitle={2012 IEEE International Conference on Wireless Information Technology and Systems (ICWITS)}, author={Trew, R. J. and Hou, D. and Schimizzi, R. and Goswami, A. and Bilbro, G. L.}, year={2012} }
 @article{trew_2012, title={Research Funding and the PROCEEDINGS OF THE IEEE Centennial}, volume={100}, ISSN={["0018-9219"]}, DOI={10.1109/jproc.2012.2190682}, journal={PROCEEDINGS OF THE IEEE}, author={Trew, Robert J.}, year={2012}, month={May}, pages={1273–1277} }
 @article{barry_sokolov_kim_trew_2010, title={Large-Signal Analysis of Terahertz Generation in Submicrometer GaN Diodes}, volume={10}, ISSN={1530-437X 1558-1748}, url={http://dx.doi.org/10.1109/JSEN.2009.2038132}, DOI={10.1109/jsen.2009.2038132}, abstractNote={The conditions for microwave power generation in a submicrometer GaN diode, with a relatively lightly doped active channel, coupled to an external resonant circuit are investigated. Applying a high-field electron transport model based on the local quasi-static approximation, we show that oscillations in group III-nitride diodes can be supported in the terahertz-frequency range near the limited space-charge accumulation regime. The shape of the diode voltage and electronic current waveforms are examined in terms of the circuit parameters and operating frequencies over the bandwidth of active generation. Based on a Fourier series analysis of the diode voltage and current, the generated power and dc-to-RF conversion efficiency at the fundamental and the second or higher order harmonic frequencies are estimated. The calculation results clearly indicate that submicrometer GaN diodes (channel doping of 1 × 1017 cm-3) can achieve large output powers (> 1 W) in the absence of Gunn domain formation, over a wide range of frequencies, near 0.5 THz.}, number={3}, journal={IEEE Sensors Journal}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Barry, E. A. and Sokolov, V. N. and Kim, K. W. and Trew, R. J.}, year={2010}, month={Mar}, pages={765–771} }
 @article{kong_sokolov_kim_trew_2010, title={Quasi-Coherent Thermal Emission in the Terahertz by Doped Semiconductors}, volume={10}, ISSN={1530-437X 1558-1748}, url={http://dx.doi.org/10.1109/JSEN.2009.2038133}, DOI={10.1109/jsen.2009.2038133}, abstractNote={We investigate thermal emission characteristics mediated by surface plasmon polaritons (SPPs) resonantly excited at a semiconductor-vacuum interface. The characteristic plasma and SPP resonant frequencies in the interval from 0.3 to 10 THz can be controlled with conventional doping densities. All of the cases under consideration (n-doped GaAs, GaN, and Si) demonstrate the spectral energy density in the near field that is several orders of magnitude larger than the blackbody radiation. The strongly resonant SPPs are also shown to enhance drastically the radiative heat transfer between two semi-infinite surfaces separated by nanometric distances. The possibility of extending spatially coherent emission through 1-D binary grating is examined based on a rigorous coupled-wave analysis. Our calculation results clearly indicate that n-doped semiconductors with properly designed surface grating can achieve efficient directional thermal emission in the THz frequency range for potential use in a number of applications including sensing.}, number={3}, journal={IEEE Sensors Journal}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Kong, B. D. and Sokolov, V. N. and Kim, K. W. and Trew, R. J.}, year={2010}, month={Mar}, pages={443–450} }
 @article{jensen_trew_woolard_gupta_theriault_hayat_li_gillespie_2010, title={Special Issue on Enhancement Algorithms, Methodologies and Technology for Spectral Sensing}, volume={10}, ISSN={["1530-437X"]}, DOI={10.1109/jsen.2010.2041385}, abstractNote={The paper is an editorial issue on enhancement algorithms, methodologies and technology for spectral sensing and serves as a valuable and useful reference for researchers and technologists interested in the evolving state-of-the-art and/or the emerging science and technology base associated with spectral-based sensing and monitoring problem. This issue is particularly relevant to those seeking new and improved solutions for detecting chemical, biological, radiological and explosive threats on the land, sea, and in the air.}, number={3}, journal={IEEE SENSORS JOURNAL}, author={Jensen, James O. and Trew, Robert J. and Woolard, Dwight L. and Gupta, Neelam and Theriault, Jean-Marc and Hayat, Majeed M. and Li, Yanqiu and Gillespie, Patti}, year={2010}, month={Mar}, pages={373–378} }
 @article{trew_green_shealy_2009, title={AlGaN/GaN HFET Reliability}, volume={10}, ISSN={["1557-9581"]}, DOI={10.1109/MMM.2009.932286}, abstractNote={High-voltage AlGaN/GaN HFETs can produce high RF output power with nearly ideal power-added efficiency. But widespread adoption of these HFETs has been limited by a lack of acceptable reliability data for practical communications and radar applications. Device problems that have been observed include dc current and RF output power degradation as a function of time when the device is operating. Sudden and permanent degradation shifts in device performance have also been observed under certain operating conditions. Identified causes of the reliability problems include the quantum mechanical tunneling of electrons on the gate electrode to the surface of the semiconductor adjacent to the gate on the drain side, and a defect generation mechanism that occurs at a high, critical electric field. The gate leakage phenomenon described in this article produces electrons on the surface of the AlGaN layer adjacent to the gate electrode, and this creates a negative charge layer that partially depletes the conducting channel, thereby producing a degradation in dc current and RF output power. The gate leakage current is present when the device is biased and driven with an RF signal, and therefore the charge accumulation increases as a function of operation time. The gate tunnel current is a very sensitive function of surface state density, particularly near the gate edge, and of the magnitude of the electric field at this location. In addition, at a critical magnitude of the electric field defects in the AlGaN layer are created due to mechanical stress on the crystal structure, and these defects act as charge trapping centers. This mechanism is not well understood at this time and is currently the subject of research and investigation. Parameters that affect reliability are a function of device design and surface processing. Improvements in device reliability have been achieved through design modifications to produce improved surface passivation layers that reduce the gate and surface leakage currents and further modifications to reduce the magnitude of the electric field internal to the device. Continuing reliability study is required to fully elucidate the link between observed degradation behavior and physical failure mechanisms in a statistically significant manner.}, number={4}, journal={IEEE MICROWAVE MAGAZINE}, author={Trew, Robert J. and Green, Daniel S. and Shealy, Jeffrey B.}, year={2009}, month={Jun}, pages={116–127} }
 @article{bilbro_hou_yin_trew_2009, title={Predicting the performance of a power amplifier using large-signal circuit simulations of an AlGaN/GaN HFET model}, volume={7216}, ISSN={["1996-756X"]}, DOI={10.1117/12.803348}, abstractNote={We have quantitatively modeled the conduction current and charge storage of an HFET in terms its physical dimensions and material properties. For DC or small-signal RF operation, no adjustable parameters are necessary to predict the terminal characteristics of the device. Linear performance measures such as small-signal gain and input admittance can be predicted directly from the geometric structure and material properties assumed for the device design. We have validated our model at low-frequency against experimental I-V measurements and against two-dimensional device simulations. We discuss our recent extension of our model to include a larger class of electron velocity-field curves. We also discuss the recent reformulation of our model to facilitate its implementation in commercial large-signal high-frequency circuit simulators. Large signal RF operation is more complex. First, the highest CW microwave power is fundamentally bounded by a brief, reversible channel breakdown in each RF cycle. Second, the highest experimental measurements of efficiency, power, or linearity always require harmonic load pull and possibly also harmonic source pull. Presently, our model accounts for these facts with an adjustable breakdown voltage and with adjustable load impedances and source impedances for the fundamental frequency and its harmonics. This has allowed us to validate our model for large signal RF conditions by simultaneously fitting experimental measurements of output power, gain, and power added efficiency of real devices. We show that the resulting model can be used to compare alternative device designs in terms of their large signal performance, such as their output power at 1dB gain compression or their third order intercept points. In addition, the model provides insight into new device physics features enabled by the unprecedented current and voltage levels of AlGaN/GaN HFETs, including non-ohmic resistance in the source access regions and partial depletion of the 2DEG in the drain access region.}, journal={GALLIUM NITRIDE MATERIALS AND DEVICES IV}, author={Bilbro, Griff L. and Hou, Danqiong and Yin, Hong and Trew, Robert J.}, year={2009} }
 @article{barry_sokolov_kim_trew_2009, title={Terahertz generation in GaN diodes operating in pulsed regime limited by self-heating}, volume={94}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.3147217}, DOI={10.1063/1.3147217}, abstractNote={The conditions for pulsed regime operation of terahertz power generation in vertical nanoscale GaN-based diodes are investigated via self-consistent simulation of the high-field electron transport in the active channel and thermal transport in the entire device structure. The combined electrothermal model allows for a detailed analysis of the dynamical local distributions of the electric field, drift-velocity, and lattice temperature. We show that stable generation is achievable with a self-heating limited output power of 2.25 W at an operation frequency of 0.71 THz for a pulse width of 3 ns with a few tens of nanosecond duty cycle.}, number={22}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Barry, E. A. and Sokolov, V. N. and Kim, K. W. and Trew, R. J.}, year={2009}, month={Jun}, pages={222106} }
 @article{woolard_trew_polla_stroscio_varshney_jensen_jensen_lugli_aono_2008, title={Nanosensors for defense and security}, volume={8}, ISSN={["1530-437X"]}, DOI={10.1109/jsen.2008.924436}, abstractNote={The 59 articles in this special issue focus on nanosensors for defense and security.}, number={5-6}, journal={IEEE SENSORS JOURNAL}, author={Woolard, Dwight L. and Trew, Robert J. and Polla, Dennis L. and Stroscio, Michael A. and Varshney, Usha and Jensen, Janet and Jensen, James O. and Lugli, Paolo O. and Aono, Masakazu}, year={2008}, pages={641–646} }
 @article{kong_sokolov_kim_trew_2008, title={Terahertz emission mediated by surface plasmon polaritons in doped semiconductors with surface grating}, volume={103}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.2840063}, DOI={10.1063/1.2840063}, abstractNote={Doped semiconductors with one-dimensional surface gratings are studied theoretically for application to terahertz emission. The presence of free carriers supports thermally excited surface plasmon polaritons at the semiconductor-vacuum interface whose resonance frequency can be controlled by doping. The calculation based on the fluctuational electrodynamics shows that the near-field spectral energy density of this surface excitation can be many orders of magnitude larger than those in the blackbody radiation. At the same time, a rigorous coupled-wave analysis with a properly designed surface microstructure clearly indicates narrow angular lobes in the directional emissivity at the targeted frequencies, illustrating strong coupling between surface plasmon polaritons and propagating waves. Thus, doped semiconductors with engineered radiation may provide an efficient terahertz source with spatial and spectral control.}, number={5}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Kong, B. D. and Sokolov, V. N. and Kim, K. W. and Trew, R. J.}, year={2008}, month={Mar}, pages={056101} }
 @article{barry_sokolov_kim_trew_2008, title={Terahertz generation in GaN diodes in the limited space-charge accumulation mode}, volume={103}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.2946717}, DOI={10.1063/1.2946717}, abstractNote={The conditions for terahertz power generation are investigated theoretically in a nanoscale GaN-based diode coupled to an external resonant circuit for operation in the limited space-charge accumulation (LSA) mode under the high-field transport regime. The generation criteria are revisited in terms of a phase plane analysis of the diode high-field transport and circuit equations. Based on a Fourier series analysis, the waveforms of the diode voltage and current are examined and the generated power and conversion efficiencies are estimated at the fundamental and lowest harmonic frequencies. The advantages of group-III nitride LSA diodes are elucidated including their ability to simultaneously achieve large output powers (>10 mW) and high dc-to-rf conversion efficiencies (>1%) over a wide range of frequencies near 1 THz.}, number={12}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Barry, E. A. and Sokolov, V. N. and Kim, K. W. and Trew, R. J.}, year={2008}, month={Jun}, pages={126101} }
 @article{sokolov_kong_kim_trew_2007, title={Quasimonochromatic emission spectra in the near field by polar semiconductor thermal sources}, volume={90}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.2713166}, DOI={10.1063/1.2713166}, abstractNote={The near-field spectra of the electromagnetic field emitted from a planar surface are theoretically investigated for a number of polar semiconductor and dielectric materials that support surface phonon polaritons. All of the studied materials, InP, GaAs, GaN, SiC, and α-Al2O3 (sapphire), exhibit quasimonochromatic thermal emission symbolized by strong peaks of evanescent modes at well-defined frequencies in the near field that correspond to the appropriate peaks in the density of states for surface phonon polaritons. It is also found that the materials with lower polariton frequencies (e.g., InP and GaAs) generally demonstrate a higher peak spectral energy density compared to those with higher frequencies (e.g., SiC). This trend is maintained over the entire range of temperature (300–600K) and the distance from the surface (⩽10μm) considered in the calculation. Thus, the results clearly indicate that among the studied materials InP and GaAs are the best candidates to provide the quasicoherent thermal emis...}, number={11}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Sokolov, V. N. and Kong, B. D. and Kim, K. W. and Trew, R. J.}, year={2007}, month={Mar}, pages={113106} }
 @article{trew_liu_bilbro_kuang_vetury_shealy_2006, title={Nonlinear source resistance in high-voltage microwave AlGaN/GaN HFETs}, volume={54}, ISSN={["0018-9480"]}, DOI={10.1109/TMTT.2006.873627}, abstractNote={Wide bandgap semiconductors are used to fabricate field-effect transistors with significantly improved RF output power compared to GaAs- and InP-based devices. Nitride-based heterostructure field-effect transistors can be biased at high drain voltages, up to and exceeding 100 V, which results in high RF output power. However, the operation of these devices at high drain bias introduces physical phenomena within the device that affect both dc and RF performance. In this study, the existence of a nonlinear source resistance due to space-charge limited current conditions is demonstrated and verified. Inclusion of the nonlinear source resistance in a physics-based device simulator produces excellent agreement between simulated and measured data. The nonlinear source resistance degrades RF performance and limits amplifier linearity.}, number={5}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Trew, RJ and Liu, YY and Bilbro, GL and Kuang, WW and Vetury, R and Shealy, JB}, year={2006}, month={May}, pages={2061–2067} }
 @article{bilbro_trew_2006, title={RF knee walkout and source access region of unpassivated HFETs}, volume={42}, DOI={10.1049/el:20062113}, abstractNote={A simple circuit model is used for the source access region of an AlGaN/GaN HFET in a microwave power amplifier to show that the interaction between gate-to-source surface current and 2DEG conductivity by itself can produce RF knee walkout.}, number={24}, journal={Electronics Letters}, author={Bilbro, G. L. and Trew, R. J.}, year={2006}, pages={1425–1427} }
 @article{trew_2005, title={High-frequency solid-state electronic devices}, volume={52}, ISSN={["0018-9383"]}, DOI={10.1109/TED.2005.845862}, abstractNote={Starting with exploratory work in the 1930s and development work in the 1940s a variety of two-terminal and three-terminal solid-state device structures have been proposed, fabricated, and developed. This work parallels the development effort on vacuum electronic devices, and the two technologies share many applications. The solid-state and vacuum electronic devices work in tandem to enable numerous commercial and military systems. Solid-state device development is closely linked to semiconductor materials growth and processing technology, and advances such as the introduction of heterojunction growth technology, permit complex multiple layer device structures to be fabricated and optimized for maximized device performance. This work has been very successful and a variety of high-performance diodes and transistors are now available for use from UHF into the millimeter-wave spectrum, approaching terahertz frequencies. The development, operating principles, and state-of-the-art of various diode and transistor structures are reviewed.}, number={5}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Trew, RJ}, year={2005}, month={May}, pages={638–649} }
 @article{trew_bilbro_kuang_liu_yin_2005, title={Microwave AlGaN/GaN HFEVs}, volume={6}, ISSN={["1527-3342"]}, DOI={10.1109/MMW.2005.1417998}, abstractNote={This article presents the operating physics, performance potential, and status of device development of microwave AlGaN/GaN heterostructure field-effect transistors. AlGaN/GaN HFETs show potential for use in improved RF performance microwave amplifier applications. Development progress has been rapid, and prototype devices have demonstrated RF output power density as high as 30 W/mm. Microwave amplifier output power is rapidly approaching 100 W for single-chip operation, and these devices may soon find application for cellular base station transmitter applications. Devices are being developed for use in X-band radars, and RF performance is rapidly improving. The HFET devices experience several physical effects that can limit performance. These effects consist of nonlinearities introduced during the high-current and high-voltage portions of the RF cycle. High-current phenomena involve the operation of the conducting channel above the critical current density for initiation of space-charge effects. The source resistance is modulated in magnitude by the channel current, and high source resistance results. High voltage effects include reverse leakage of the gate electrode and subsequent charge trapping effects on the semiconductor surface, and RF breakdown in the conducting channel. These effects can produce premature saturation effects. Also, under certain conditions, high voltage operation of the device can initiate an IMPATT mode of operation. When this occurs, the channel current increases and RF gain is increased. This phenomenon enhances the RF output power of the device. The physical limiting effects can be controlled with proper design, and the outlook for use of these devices in practical applications is excellent.}, number={1}, journal={IEEE MICROWAVE MAGAZINE}, author={Trew, RJ and Bilbro, GL and Kuang, W and Liu, Y and Yin, H}, year={2005}, month={Mar}, pages={56–66} }
 @article{trew_woolard_2005, title={Special issue on blue sky electronic technologies}, volume={93}, ISSN={["0018-9219"]}, DOI={10.1109/JPROC.2005.855454}, number={10}, journal={PROCEEDINGS OF THE IEEE}, author={Trew, RJ and Woolard, DL}, year={2005}, month={Oct}, pages={1687–1690} }
 @misc{mishra_trew_1993, title={Method of making high current, high voltage breakdown field effect transistor}, volume={5180681}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Mishra, U. K. and Trew, R. J.}, year={1993} }
 @misc{mishra_trew_1992, title={High current, high voltage breakdown field effect transistor}, volume={5084743}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Mishra, U. K. and Trew, R. J.}, year={1992} }
 @article{trew_yan_mock_1991, title={THE POTENTIAL OF DIAMOND AND SIC ELECTRONIC DEVICES FOR MICROWAVE AND MILLIMETER-WAVE POWER APPLICATIONS}, volume={79}, ISSN={["0018-9219"]}, DOI={10.1109/5.90128}, abstractNote={The potential of SiC and diamond for producing microwave and millimeter-wave electronic devices is reviewed. It is shown that both of these materials possess characteristics that may permit RF electronic devices with performance similar to or greater than what is available from devices fabricated from the commonly used semiconductors, Si, GaAs, and InP. Theoretical calculations of the RF performance potential of several candidate high-frequency device structures are presented: the metal semiconductor field-effect transistor (MESFET), the impact avalanche transit-time (IMPATT) diode, and the bipolar junction transistor (BJT). Diamond MESFETs are capable of producing over 200 W of X-band power as compared to about 8 W for GaAs MESFETs. Devices fabricated from SiC should perform between these limits. Diamond and SiC IMPATT diodes also are capable of producing improved RF power compared to Si, GaAs, and InP devices at microwave frequencies. RF performance degrades with frequency and only marginal improvements are indicated at millimeter-wave frequencies. Bipolar transistors fabricated from wide bandgap material probably offer improved RF performance only at UHF and low microwave frequencies. >}, number={5}, journal={PROCEEDINGS OF THE IEEE}, author={TREW, RJ and YAN, JB and MOCK, PM}, year={1991}, month={May}, pages={598–620} }