GaN High Electron Mobility Transistors Research Articles

Improved drain lag by reduced surface current in GaN HEMT via an ultrathin HfO2 blanket layer

This paper reports the influence of an ultrathin 1.5 nm atomic-layer-deposited HfO2 blanket layer as a gate dielectric on GaN high-electron-mobility transistors (HEMTs) grown on a 4H-SiC substrate. Transistors with a gate length of 250 nm and a source-to-drain distance of 3 µm were manufactured. The proposed technique involves HfO2 deposition at 250 ∘C prior to the gate metallization with no additional lithography steps. This approach reduced the drain lag by 83% compared to the conventional design with no gate dielectric. The HfO2 layer suppressed the parasitic lateral conduction from the gate, reduced surface trapping, and improved gate electrostatics. The manufactured devices exhibited nearly three orders of magnitude decreased surface leakage, better turn-on behavior, and improved cut-off frequency f T linearity by 16%. High quality metal-oxide interface formation was confirmed by the conductance method. Results demonstrate that the blanket HfO2 deposition is a promising approach to improve the current dispersion characteristics and gate electrostatics of GaN HEMTs without incurring major changes to the established fabrication techniques.

Effects of GaN channel downscaling in AlGaN–GaN high electron mobility transistor structures grown on AlN bulk substrate

In this work, two series of AlGaN/GaN/AlN high electron mobility transistor (HEMT) heterostructures have been grown by molecular beam epitaxy on AlN bulk substrates. The effects of reduction in the GaN channel thickness as well as the AlGaN barrier thickness and composition on structural and electrical properties of the heterostructures have been studied. The material analysis involved high-resolution x-ray diffraction, atomic force microscopy, and cross-sectional transmission electron microscopy. In a first series of HEMT structures grown with an aluminum content of 30% in the AlGaN barrier, the channel downscaling results in a reduction in the GaN strain relaxation rate but at the expense of degradation in the mean crystal quality and in the electron mobility with a noticeable increase in the sheet resistance. An opposite trend is noticed for the three-terminal breakdown voltage of transistors, so that a trade-off is obtained for a 50 nm width GaN channel HEMT, which exhibits a sheet resistance of 1700 Ω/sq. with transistors demonstrating three-terminal breakdown voltage up to 1400 V for 40 μm gate to drain spacing with static on resistance Ron = 32 mΩ cm2. On the other hand, a second series of HEMT structures with high aluminum content AlGaN barriers and sub-10 nm GaN channels have been grown perfectly strained with high sheet carrier densities allowing to preserve sheet resistances in the range of 880–1050 Ω/sq.

A Comprehensive Overview of the Temperature-Dependent Modeling of the High-Power GaN HEMT Technology Using mm-Wave Scattering Parameter Measurements

The gallium-nitride (GaN) high electron-mobility transistor (HEMT) technology has emerged as an attractive candidate for high-frequency, high-power, and high-temperature applications due to the unique physical characteristics of the GaN material. Over the years, much effort has been spent on measurement-based modeling since accurate models are essential for allowing the use of this advanced transistor technology at its best. The present analysis is focused on the modeling of the scattering (S-) parameter measurements for a 0.25 μm GaN HEMT on silicon carbide (SiC) substrate at extreme operating conditions: a large gate width (i.e., the transistor is based on an interdigitated layout consisting of ten fingers, each with a length of 150 μm, resulting in a total gate periphery of 1.5 mm), a high ambient temperature (i.e., from 35 °C up to 200 °C with a step of 55 °C), a high dissipated power (i.e., 5.1 W at 35 °C), and a high frequency in the millimeter-wave range (i.e., from 200 MHz up to 65 GHz with a step of 200 MHz). Three different modeling approaches are investigated: the equivalent-circuit model, artificial neural networks (ANNs), and gated recurrent units (GRUs). As is shown, each modeling approach has its pros and cons that need to be considered, depending on the target performance and their specifications. This implies that an appropriate selection of the transistor modeling approach should be based on discerning and prioritizing the key features that are indeed the most important for a given application.

Ti3 C2 Tx MXene van der Waals gate contact for GaN high electron mobility transistors.

Gate controllability is a key factor that determines the performance of GaN high electron mobility transistors (HEMTs). However, at traditional metal-GaN interface, direct chemical interaction between metal and GaN can result in fixed charges and traps, which can significantly deteriorate the gate controllability. In this study, Ti3 C2 Tx MXene films were integrated into GaN HEMTs as the gate contact, wherein van der Waals heterojunctions were formed between MXene films and GaN without direct chemical bonding. The GaN HEMTs with enhanced gate controllability exhibited an extremely low off-state current (IOFF ) of 10-7 mA/mm, a record high ION /IOFF current ratio of ∼1013 (which is six orders of magnitude higher than conventional Ni/Au contact), a high off-state drain breakdown voltage of 1085V, and a near-ideal subthreshold swing of 61mV/dec. This work shows the great potential of MXene films as gate electrodes in wide-bandgap semiconductor devices. This article is protected by copyright. All rights reserved.

Electrical Characteristics of Gated Anode Diodes Based on Normally Off Recessed‐Gate GaN High‐Electron‐Mobility Transistors for Rectenna Applications

AlGaN/GaN high‐electron‐mobility transistor (HEMT)‐based gated‐anode diodes (GADs) for a 5.8 GHz rectenna application are proposed. An anode of the GAD is formed by connecting a gate and a drain of a normally off GaN HEMT. Herein, a wide recessed HEMT structure reported in the previous article is modified to a buried‐type recessed gate HEMT structure. The gate‐to‐cathode distance is optimized to maximize device performance. Typical direct current (DC) characteristics of the HEMTs are a threshold voltage (Vth) of +0.4 V and a maximum drain current (Imax) of 450 mA mm−1. GADs using the HEMTs show the characteristics of maximum forward current (If) of 600 mA mm−1and reverse breakdown voltage (BVr) of more than 100 V. The GAD using the recessed gate structure HEMT is shown to significantly improveIfandBVrsimultaneously compared to the previous work using the wide recessed gate structure. The rectifying performance of a bridge‐type rectifier simulated with SPICE model of the GAD shows radio frequency (RF)–DC conversion efficiency of 84% and RF input power of 13 W at 5.8 GHz using four GADs with each gate width (Wg) of 400 μm.

Total-ionizing dose irradiation induced degradation behavior and mechanism of the Cascode GaN HEMTs

In this article, the effects of total ionizing dose (TID) irradiation and the annealing treatment on the degradation of the commercial Cascode GaN high-electron-mobility transistors (HEMTs) were investigated, and low frequency noise method (LFN) was carried out to analyze the defects. The DC characteristics show that the device after TID irradiation with different doses exhibits a negative drift of threshold voltage (V th) and a remarkable increase of drain-source current (I ds) with respect to the fresh one. Meanwhile, with increasing doses of the TID irradiation, the off-state drain leakage current increases, while the drain-source resistance decreases. The gate-lag characteristic gets better for the Cascode GaN HEMTs after TID irradiation. The transfer characteristics, output characteristics, blocking characteristics and capacitance characteristics of the devices can partly be restored by annealing treatment, but there is no pronounced influence on the gate-lag characteristics and drain-source resistance. The trap density extracted by the LFN method decreases in the Cascode GaN HEMTs after TID irradiation. The degradation behavior and mechanism of the Cascode GaN HEMTs under TID irradiation are analyzed. The experimental results may provide a useful reference for the design and space application of the Cascode GaN HEMTs.

RF linearity trade-offs for varying T-gate geometries of GaN HEMTs on Si

AbstractShort-channel Gallium Nitride (GaN) high-electron-mobility transistors (HEMTs) often utilize T-shape gates due to their large gate-line cross-sectional area and subsequent fMAX increase. In this paper, we report the linearity trade-offs associated with varying the T-gate geometries of AlGaN/GaN HEMTs on Si, specifically the gate extensions which serve as field plates and their impact on the large-signal performance. Small-signal characterization and modeling, in addition to TCAD, provide initial guidelines for the optimal dimensions for the gate field plates using the ratio of fT and the product of the gate resistance and the gate-to-drain capacitance. We utilize various characterization methods, including 6 GHz non-linear vector network analyzer characterization in addition to load-pull, to quantify the amplitude and phase distortion and their subsequent impact on the large-signal metrics of the devices under differing matching conditions and bias points. We deduce that the influence of the gate field plates on the amplitude and phase distortion is non-negligible, particularly under matched conditions.

The GaN Breakthrough for Sustainable and Cost-Effective Mobility Electrification and Digitalization

Vehicle electrification and digitalization are even more and more increasingly pushed by several aims, such as the improvement in sustainability, wellness, safety, and reliability. The need for onboard power electronics is a common factor for the different types of electric vehicles. Similarly, the increasing presence of onboard Internet of Things items as well as systems implementing artificial intelligence asks for additional power electronics that ensure supplying them according to their rating plate. Additionally, power converters have to perform this task also for traditional loads (infotainment; climate control, and so on) and new ones (USB and wireless chargers; Light detection and ranging, LiDAR applications, and so on). The transaction towards full electrification and digitalization requires highly efficient and compact power electronics converters. In this perspective, the Gallium nitride (GaN) high-electron-mobility transistors (HEMTs) are the best enabler device technology. This paper analyses the current and prospective improvement in sustainability and cost achievable with GaN in the automotive sector. Then, the advantages of the system in package GaN devices in power converter supporting this transaction, such as 48 V–12 V converters, onboard charges, and cell phone wireless chargers are experimentally investigated. The results have highlighted that, already in 2023, the use of Si devices in these applications does not enable further a lower overall converter cost with respect to GaN-based solutions. The reduction of passive costs enabled by using higher frequency thanks to the GaN features compensates for its higher cost. On the other hand, GaN HEMT enables high efficiency in all the aforesaid automotive applications as also experimentally proved in this paper, making it the best solution in terms of sustainability.

Research Progress in Capping Diamond Growth on GaN HEMT: A Review

With the increased power density of gallium nitride (GaN) high electron mobility transistors (HEMTs), effective cooling is required to eliminate the self-heating effect. Incorporating diamond into GaN HEMT is an alternative way to dissipate the heat generated from the active region. In this review, the four main approaches for the integration of diamond and GaN are briefly reviewed, including bonding the GaN wafer and diamond wafer together, depositing diamond as a heat-dissipation layer on the GaN epitaxial layer or HEMTs, and the epitaxial growth of GaN on the diamond substrate. Due to the large lattice mismatch and thermal mismatch, as well as the crystal structure differences between diamond and GaN, all above works face some problems and challenges. Moreover, the review is focused on the state-of-art of polycrystalline or nanocrystalline diamond (NCD) passivation layers on the topside of GaN HEMTs, including the nucleation and growth of the diamond on GaN HEMTs, structure and interface analysis, and thermal characterization, as well as electrical performance of GaN HEMTs after diamond film growth. Upon comparing three different nucleation methods of diamond on GaN, electrostatic seeding is the most commonly used pretreatment method to enhance the nucleation density. NCDs are usually grown at lower temperatures (600–800 °C) on GaN HEMTs, and the methods of “gate after growth” and selective area growth are emphasized. The influence of interface quality on the heat dissipation of capped diamond on GaN is analyzed. We consider that effectively reducing the thermal boundary resistance, improving the regional quality at the interface, and optimizing the stress–strain state are needed to improve the heat-spreading performance and stability of GaN HEMTs. NCD-capped GaN HEMTs exhibit more than a 20% lower operating temperature, and the current density is also improved, which shows good application potential. Furthermore, the existing problems and challenges have also been discussed. The nucleation and growth characteristics of diamond itself and the integration of diamond and GaN HEMT are discussed together, which can more completely explain the thermal diffusion effect of diamond for GaN HEMT and the corresponding technical problems.

Exploring Gallium Nitride as a Viable Replacement for High Power and Performance Semiconductors: A Comparative Study of Electrical Properties and Fabrication Techniques

The semiconductor industry is continuously seeking to develop more compact, faster, and less expensive transistors allowing for more power to be packed into the same chip. This requires the development of smaller and more efficient semiconductors that are currently in the range of around 5-7 nanometers each. However, the limitations of silicon, the leading semiconductor material, are becoming more apparent, prompting exploration of other compounds, with a very promising candidate being gallium nitride (GaN). This paper presents an overview of GaN-based high electron mobility transistors (HEMTs) and integrated circuits (ICs), which offer several advantages over silicon-based counterparts. GaN HEMTs have lower on-resistance, faster devices, less capacitance, and less power consumption allowing them to sustain higher voltages and faster current. Meanwhile, GaN-based ICs have the potential to improve the efficiency of power conversion systems and circuits due to their ability to integrate both power-level and signal-level devices on the same wafer. With GaN-based devices, power conversion can become more efficient and cost-effective, ushering a new era for power conversion.

Techniques for Adaptive Input-Power Distribution in Doherty Power Amplifier and Load Modulation of Its Driver-Stage Power Amplifier

Techniques for adaptive input-power distribution in Doherty power amplifier (DPA) with the modified Wilkinson power divider and load modulation of its driver-stage PA are described. Combination of these techniques improves the linearity and efficiency of the two-stage PA with DPA as a final stage. Both the techniques leverage the nonlinearity of the input impedance of the auxiliary power amplifier in the DPA. The first technique is applied to a 3.5-GHz 32-W single-stage DPA using GaN high electron mobility transistor (HEMT) devices. Evaluation results showed that by using the technique, adjacent channel leakage ratio (ACLR) improvement of 9 dB was obtained under 8.5-dB peak to average power ratio (PAPR) 10-MHz long-term evolution (LTE) signal without digital predistortion (DPD), and the demonstrator achieved an average drain efficiency (DE) of 55% and ACLR of −50 dBc with DPD. Using the same DPA as a final stage, a two-stage PA was also designed and fabricated to verify the second technique. Due to the load modulation of the driver stage PA, efficiency improvement of 2.6% for the two-stage power added efficiency (PAE) is confirmed by simulation, and the demonstrator achieved a two-stage PAE of 45.4% under 8.5-dB PAPR 20-MHz LTE signal with ACLR of −50 dBc with DPD.

Comparisons and Evaluations of Silicon and Wide Band Gap Devices at Cryogenic Temperature

In this article, the static and dynamic characterizations for semiconductors with different materials, including silicon (Si), silicon carbide (SiC), and gallium nitride (GaN), are evaluated and compared at room temperature and cryogenic temperature (liquid nitrogen temperature). For static characterizations, the on-state resistance and threshold voltage are evaluated. For dynamic characterizations, the turn-on switching loss, turn-off switching loss, and dynamic on-state resistance ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds(on)</sub> ) are evaluated. The results demonstrate that Si and GaN based semiconductors have improved performances with lower on-state resistance and faster switching speed at low temperature operations. For SiC based semiconductors, the on-state resistance increases significantly at cryogenic temperature. The switching speed is reduced dramatically for the evaluated 1.2 kV SiC metal oxide semiconductor field effect transistors (MOSFETs) at cryogenic temperature. This makes it less attractive for cryogenic applications. For the evaluated 650 V and 900 V SiC MOSFETs, the switching speed remains almost unchanged at low temperature. GaN high electron mobility transistor (HEMT) demonstrates a fast turn-on switching speed at low temperature, where the device's <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">di/dt</i> are almost doubled when compared with room temperature. In addition, the dynamic <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds(on)</sub> of the evaluated GaN HEMTs also decreases at low temperatures. The evaluation results can serve as guidelines for cryogenic power electronics applications. Meanwhile, the future work for semiconductors cryogenic characterizations is discussed.

Short Circuits in GaN HEMTs: Test Bench Setup and Characterization

In this article, a setup to characterize the failure mechanisms and degradation indicators of gallium nitride (GaN) high-electron-mobility transistors (HEMTs) under short-circuit events is presented. Understanding how this technology fails is critical, especially for space applications where a common failure mechanism is the short-circuit event due to radiation. First, the previous literature in the field is reviewed. Both the behavior under single and repetitive short circuits and failure mechanisms are discussed. Then, a systematic method is proposed to measure the critical electrical parameters and analyze the behavior of the device under test under short-circuit failure to build a reliability model. A setup to characterize GaN HEMT devices is developed, and using it, multiple tests and short circuits have been performed to characterize the devices under test at different conditions and to identify critical parameters and aging indicators. The reliability challenge of GaN devices could be addressed by having on-board in-system prognostics and device health monitoring techniques to predict device failures well ahead of time.

Investigation on Fe-Doped AlGaN/GaN HEMT at 148 GHz Using E-FPL Technology for High-Frequency Communication Systems

In this research work, design of the Extended Field Plate Length (E-FPL) T-gate with Fe doped AlGaN buffer structure on the graded Aluminum Gallium nitride (AlGaN)/ Gallium nitride (GaN) high electron mobility transistor (HEMT) is proposed. The gate length of 60 nm with an ExFPL up to 50 nm towards the drain shows remarkable improvement in breakdown voltage. Meanwhile, the drain current (IDS) and transconductance (GM) is further improved by the Fe doped AlGaN Buffer design. In radio frequency (RF) small signal analysis this device exhibits a peak current-gain cutoff frequency fT of 148 GHz. This device has improved transconductance of 24% with high frequency has compared with conventional GaN HEMT device. It is highly compatible with military applications such as Radio Frequency (RF) upstream transmitters, ship and aircraft communication transmitters and High-frequency Radars (HFRs).

Theoretical Prediction of Mobility Improvement in GaN-Based HEMTs at High Carrier Densities

In this article, we use a semiclassical low-field mobility modeling framework, which includes all relevant scattering mechanisms, to examine the dependence of electron mobility on 2-D electron gas (2DEG) density in previously characterized high Al-content AlGaN/gallium nitride (GaN) high electron mobility transistors (HEMTs) with and without an AlN spacer layer. Polar optical phonon (POP) scattering has previously been identified as the dominant scattering mechanism in GaN-based HEMTs at room temperature, so the analysis of POP scattering rates is of particular importance. We find that the POP-limited mobility in both structures decreases with increasing 2DEG density up to a critical density of around <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${10}^{{13}}$ </tex-math></inline-formula> cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{2}}$ </tex-math></inline-formula> , above which we observe a significant improvement of up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${46}\%$ </tex-math></inline-formula> , contrary to the behavior typically reported for GaN HEMT structures. The POP-limited mobility increase is explained by the interplay of ground-state energy and quasi-Fermi energy within the channel, by which intrasubband POP emission within the ground state is suppressed at high 2DEG densities. This provides a universal guideline for the design and operation of GaN-based HEMTs to achieve a minimum ON-resistance in switching applications at room temperature and above.

On GaN Low Noise Amplifier: Device Modelling and Circuit Design

The radio frequency spectrum is currently congested due to the advancement in wireless communication systems. For these system, low noise-figure linear amplifier is crucially needed to design the front-end receiver and amplify very low-power received signals without significantly degrading their qualities. Gallium Nitride (GaN) High Electron Mobility Transistor (HEMT) has wider linear dynamic range and thus represents an excellent alternative for designing highly linear Low Noise Power Amplifier (LNA). Also, GaN as a wide bandgap material could be very optimistic to work in harsh and noisy environment such as earth space for satellite communications. In this work, global optimization technique-based noise-models are presented and then used to design LNAs. An extensive review of state-of-the-art GaN HEMT based low noise amplifier is given in this paper. Then different topologies of the low noise amplifier are explored. The techniques of bandwidth enhancement are also reviewed. The design of low noise amplifiers using the developed GaN HEMT model is done at X and K bands of frequencies. The performances of the designed LNAs are compared with state-of-the-art reported LNAs in terms of the Noise Figure (NF), gain and bandwidth. The paper presented very interesting results for the cascade, which exhibited the best NF of 1.6-2 dB and a gain of 14.5-16.4 dB within a bandwidth of 9 to 11 GHz. The highest gain of 25-27 dB was achieved by the quadrature cascode LNA with slightly higher NF of 2.1-2.5 at an operating frequency of 8-12 GHz.

Numerical Investigation of GaN HEMT Terahertz Detection Model Considering Multiple Scattering Mechanisms.

GaN high-electron-mobility transistor (HEMT) terahertz (THz) detectors have been widely studied and applied in the past few decades. However, there are few reports about the influence of GaN/AlGaN heterostructure material properties on the detection model at present. In this paper, a response voltage model for a GaN HEMT THz detector that considers the carrier scattering in a GaN/AlGaN heterostructure is proposed. The phonon scattering, dislocation scattering, and interface roughness scattering mechanisms are taken into account in the classic THz response voltage model; furthermore, the influence of various material parameters on the response voltage is studied. In a low-temperature region, acoustic scattering plays an important role, and the response voltage drops with an increase in temperature. In a high temperature range, optical phonon scattering is the main scattering mechanism, and the detector operates in a non-resonant detection mode. With an increase in carrier surface density, the response voltage decreases and then increases due to piezoelectric scattering and optical phonon scattering. For dislocation and interface roughness scattering, the response voltage is inversely proportional to the dislocation density and root mean square roughness (RMS) but is positively related to lateral correlation length. Finally, a comparison between our model and the reported models shows that our proposed model is more accurate.

Analysis of Dead-Time Energy Loss in GaN-Based TCM Converters With an Improved GaN HEMT Model

For gallium nitride (GaN) based triangular current mode (TCM) applications, the dead-time has a significant effect on the switching loss. However, previous GaN high electron mobility transistor (HEMT) models focus on the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on/off</small> process without fully considering the effect of the dead-time. Hence, this article analyzes the switching transients under the superfluous and insufficient dead-time and evaluates the dead-time loss with an improved GaN HEMT model. The proposed model improves an existing GaN HEMT model by adding the voltage rising/falling time of the gate driver, the dynamic threshold voltage of Schottky-type GaN HEMTs, and an equivalent gate-drain capacitance obtained from the datasheet. Verified by a GaN-based double-pulse test, the proposed model can more accurately calculate the gate-source voltage and the self-commutated reverse conduction voltage. Verified by a GaN-based TCM Buck converter, the proposed model can predict the dead-time loss well and has higher simulation accuracy for the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> process induced by the inappropriate dead-time.

Experimentally Validated Gate-Lag Simulations of AlGaN/GaN HEMTs Using Fermi Kinetics Transport

This article presents for the first time a direct connection between gate lag observed in drain current transient measurements of gallium nitride (GaN) high-electron-mobility transistors (HEMTs) and traps located in the barrier of the transistor epitaxy. Semiclassical numerical simulations are presented using the Air Force Research Laboratory’s (AFRL’s) Fermi kinetics transport (FKT) solver and are validated with drain current transient measurements. Capacitance–voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${C} - {V}$ </tex-math></inline-formula> ) and conductance–voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${G} - {V}$ </tex-math></inline-formula> ) measurements are also presented to provide further insights into the trap location used in the FKT simulations. These simulations indicate that equivalent defects located specifically at the AlGaN barrier/GaN cap interface of an AFRL GaN HEMT with a density of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7.5\times 10^{{12}}$ </tex-math></inline-formula> cm−2 and positioned 1.464 eV below the GaN cap conduction band edge were the salient traps linked to the gate-lag phenomenon. The study highlights the importance of experimentally benchmarked device simulation for trapping analysis in GaN HEMTs and may provide significant insights into device engineers for mitigating trapping effects in state-of-the-art GaN technologies.

Bias Dependence of Non-Fourier Heat Spreading in GaN HEMTs

In this article, self-heating in gallium nitride (GaN) high-electron-mobility transistors (HEMTs) is studied by combining the technology computer-aided design (TCAD) and phonon Monte Carlo (MC) simulations. The simulation results indicate that the bias-dependent heat generation in the channel can have a remarkable impact on the thermal spreading process and the phonon ballistic effects simultaneously. Based on the two-heat-source model, we propose a two-thermal-conductivity model to predict the device junction temperature with the consideration of bias-dependent phonon transport in the HEMT. The proposed model is easy to be coupled with the finite-element method (FEM)-based thermal analysis without the need for time-consuming multiscale electrothermal simulations.