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Thermal Analysis of AlGaN/GaN High-Electron-Mobility Transistors with Graphene
摘要： A thermal analysis of AlGaN/GaN high electron mobility transistors (HEMTs) with Graphene is investigated using Silvaco and Finite Element Method. Two thermal management solutions are adopted; first of all, graphene is used as dissipation material between SiC substrate and GaN buffer layer to reduce thermal boundary resistance of the device. At the same time, graphene is also used as a thermal spread material on the top of the source contacts to reduce thermal resistance of the device. The thermal analysis results show that the temperature rise of device adopting graphene decreases by 46.5% in transistors operating at 13.86 W/mm. Meanwhile, the thermal resistance of GaN HEMTs with graphene is 6.8 K/W, which is much lower than the device without graphene, which is 18.5 K/W. The thermal management solutions are useful for integration of large-scale graphene into practical devices for effective heat spreading in AlGaN/GaN HEMT.
关键词： AlGaN/GaN,Thermal Management,High-Electron-Mobility Transistors (HEMTs),Graphene
更新于2025-09-23 15:23:52
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Experimental Evaluation and Analysis of Switching Transient's Effect on Dynamic On-Resistance in GaN HEMTs
摘要： The dynamic on-resistance is problematic as it can impair the converter's efficiency due to the increased conduction loss. In this paper, the hard-switching transient's effect on the dynamic on-resistance is, for the first time, evaluated experimentally on a commercial high-voltage GaN HEMT. A new R_dyn-ds,on measurement circuit with fast sensing speed is designed, and an accurate measurement of R_dyn-ds,on can be realized experimentally within 49.6 ns after the device's current reaches to the load current. A double-pulse-test setup is designed to comprehensively evaluate the switching transient's effect on R_dyn-ds,on under different operating conditions. From the experimental results, it is found that the turn-on and turn-off gate resistance have a significant impact on the dynamic on-resistance whereas the cross-talk effect on R_dyn-ds,on is negligible. Specifically, at 400 V/25 A, more than 27% (28.2%) increase in R_dyn-ds,on is observed when the external turn-on (turn-off) gate resistance increases from 0 Ω to 20 Ω. Detailed discussion and quantitative analysis are provided to explain the experimental results. In terms of the turn-on process, it is concluded that the R_dyn-ds,on variation is mainly caused by the different numbers of generated hot electrons. For the turn-off transient, it is confirmed the variation of drain current at different dv/dt slew rate leads to the R_dyn-ds,on difference.
关键词： switching transients,Dynamic on-resistance,GaN HEMTs,hot electrons
更新于2025-09-23 15:22:29
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Assessment of Self-Heating Effects Under Lateral Scaling of GaN HEMTs
摘要： The impact on self-heating mechanisms observed in GaN HEMTs fabricated on Si substrates is studied by means of a cellular Monte Carlo particle-based device simulator. Within this framework, the thermal effects are included through an energy-balance equation for phonons allowing for self-consistently coupling the charge and heat transport. First, the advanced electrothermal model of an experimental device is developed and calibrated to measured dc characteristics, showing an accurate description throughout the IDS(VGS?VDS) space, as a result of capturing the temperature dependence of the scattering processes that modify the charge transport. Then, the model is used to assess the effect of lateral scaling, i.e., reducing the source-to-gate LSG and gate-to-drain LGD dimensions, in terms of detailed temperature maps obtained for the acoustic and optical phonon modes as well as the electric field and carrier velocity profiles. It is found that the hot spot in the channel is not located at the peak electric field as predicted by previous methods, but instead, it is shifted toward the drain up to 32 nm. Furthermore, it is shown that, while scaled devices offer improved dc and small-signal ac performance, they are subjected to temperatures up to 15% higher in the channel as compared to the original nonscaled device when dissipating the same dc power, and the temperature distribution throughout the device shows a strong correlation with the scaled layout.
关键词： reliability,HEMTs,Monte Carlo methods,self-heating,scaling,GaN
更新于2025-09-23 15:22:29
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A voltage-transient method for characterizing traps in GaN HEMTs
摘要： Trapping e?ects in GaN HEMTs still limit their performance. The current-transient methodology has shown advantages in characterizing traps in the device. However, the voltage drift may cause errors in measurements with high accuracy requirements. In this paper, we present a methodology to characterize traps in GaN HEMTs using the voltage-transient measurements. We demonstrate the advantages of this method in terms of simplicity and e?ectiveness. In particular, it avoids the said problem due to the optimized measuring circuit. With this method, we have identi?ed the time constants and energy levels of traps in the AlGaN barrier layer and the GaN bu?er layer, respectively, in the devices. Their trapping and de-trapping mechanisms were also demonstrated at various temperature measurements. A classic exponential dependence of the degradation rate on the channel current was identi?ed.
关键词： Trapping e?ect,GaN,Voltage transient,High electron mobility transistors (HEMTs)
更新于2025-09-23 15:22:29
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Mechanism of leakage current increase in p-GaN gate AlGaN/GaN power devices induced by ON-state gate bias
摘要： An increase in OFF-state leakage current in p-GaN gate AlGaN/GaN high-electron-mobility transistors (HEMTs), induced by ON-state gate bias, was observed and reported in this paper. Higher OFF-state leakage current was observed with higher gate bias voltage and longer bias duration. We propose that the initial increase in OFF-state leakage current and its subsequent decay with time are due to persistent photoconductivity effects in GaN induced by hole injection and electroluminescence during the ON-state gate bias. At room temperature, it took more than 20 s for the increased leakage current to reduce to its equilibrium level in the dark. The related physical mechanisms underlying this phenomenon in the p-GaN gate HEMT structure are also proposed.
关键词： p-GaN gate,AlGaN/GaN HEMTs,persistent photoconductivity,leakage current,electroluminescence
更新于2025-09-23 15:21:01
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Real-time visualization of GaN/AlGaN high electron mobility transistor failure at off-state
摘要： Degradation and failure phenomena in high electron mobility transistors (HEMTs) are complex functions of electrical, thermal, and mechanical stresses as well as the quality of the device materials and their interfaces. Thus, it is difficult to predict or identify the dominant mechanism under various test protocols adopted in the literature. We propose that real-time visualization of the device microstructure can shift this paradigm. This is demonstrated by operating electron transparent AlGaN/GaN HEMTs inside a transmission electron microscope (TEM). Through the bright-field, diffraction, and energy dispersive spectroscopy techniques, we show that it is possible to characterize the lattice defects and diffusion of the various elements and thus monitor the micro-structural quality during the transistor failure. Off-state failure studies in the TEM clearly show the critical role of defects and interfaces that lead to punch-through mechanisms at the drain and even source sides. The 'seeing while measuring' approach presented in this study can be useful in pinpointing the dominant failure mechanisms and their fundamental origin.
关键词： GaN HEMTs,energy dispersive spectroscopy,lattice defects,transmission electron microscope,off-state failure,real-time visualization
更新于2025-09-23 15:21:01
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Discrete-Pulsed Current Time Method to Estimate Channel Thermal Resistance of GaN-Based Power Devices
摘要： A simple electrical method to extract device channel thermal resistance in transistors is presented here. The method compares the dc to discrete-pulsed characteristics and estimates the effective increase in channel temperature under dc biasing conditions. Using the discrete-pulsed I versus t method, the self-heating of the device is effectively eliminated, which helps avoiding the underestimation of the device channel thermal resistance, therefore, making it possible to perform thermal measurements at the high power operation. This technique was applied to lateral GaN HEMTs with three different substrates as well as vertical GaN current aperture vertical electron transistor (CAVET) on sapphire, which proved its sensitivity and validity for different device structures and geometries.
关键词： high-electron mobility transistors (HEMTs),self-heating,current aperture vertical electron transistor (CAVET),Channel thermal resistance
更新于2025-09-23 15:21:01
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Interface charge engineering in down-scaled AlGaN (<6a??nm)/GaN heterostructure for fabrication of GaN-based power HEMTs and MIS-HEMTs
摘要： The physical mechanism for recovery of 2D electron gas (2DEG) in down-scaled AlGaN/GaN heterostructures with SiNx layers grown by low-pressure chemical vapor deposition (LPCVD) was investigated by means of Hall-effect characterization, scanning Kelvin probe microscopy (SKPM), and self-consistent Poisson–Schr€odinger calculations. Observations using SKPM show that the surface potential of the AlGaN/GaN heterostructure remained nearly unchanged ((cid:2)1.08 eV) as the thickness of the AlGaN barrier was reduced from 18.5 to 5.5 nm and likely originated from the surface pinning effect. This led to a signi?cant depletion of 2DEG from 9.60 (cid:3) 1012 to 1.53 (cid:3) 1012 cm(cid:4)2, as determined by Hall measurements, toward a normally OFF 2DEG channel. Based on a consistent solution of the Schr€odinger–Poisson equations and analytical simulations, approximately 3.50 (cid:3) 1013 cm(cid:4)2 of positive ?xed charges were con?rmed to be induced by a 20-nm LPCVD-SiNx passivation over the AlGaN/GaN heterostructures. The interface charge exerted a strong modulation of band bending in the down-scaled AlGaN/GaN heterostructure, contributing to the ef?cient recovery of 2DEG charge density ((cid:2)1.63 (cid:3) 1013 cm(cid:4)2). E-mode ultrathin-barrier AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors with a low ON-resistance (RON), high ON/OFF current ratio, and steep subthreshold slope were implemented using LPCVD-SiNx passivation.
关键词： AlGaN/GaN heterostructure,power HEMTs,LPCVD-SiNx passivation,2D electron gas,MIS-HEMTs,interface charge engineering
更新于2025-09-23 15:19:57
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[IEEE 2019 International Conference on Electrical, Electronics and Computer Engineering (UPCON) - ALIGARH, India (2019.11.8-2019.11.10)] 2019 International Conference on Electrical, Electronics and Computer Engineering (UPCON) - A Study on the Influence of Open Circuit Voltage (Voc) and Short Circuit Current (Isc) on Maximum Power Generated in a Photovoltaic Module/Array
摘要： A technique is described, to efficiently evaluate the reliability of an RF semiconductor device when several different mechanisms contribute simultaneously to its wearout. This is of interest for present-day GaN HEMT devices because symptoms of several simultaneous degradation mechanisms have been reported widely. The technique involves first finding DC parameters that are “signatures” of each mechanism. Then, separate DC-stress lifetests are performed to find the degradation rates for the signature parameters, at several temperatures, and the corresponding Arrhenius curves. Next, an RF-stress lifetest (with only one stress condition) is performed, while monitoring all of the signature parameters and the RF performance. This is utilized to determine the “scaling factors” between the rates of change in the DC lifetests and the rates of change in the RF application. Applying these scaling factors to the original Arrhenius curves gives an “overall” Arrhenius plot for the RF application with several different lines, for the different degradation mechanisms. The technique can be extended to further degradation mechanisms, by conducting further DC and RF lifetests while monitoring appropriate signature parameters.
关键词： semiconductor device reliability,lifetesting,gallium nitride,HEMTs,Failure analysis
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE International Ultrasonics Symposium (IUS) - Glasgow, United Kingdom (2019.10.6-2019.10.9)] 2019 IEEE International Ultrasonics Symposium (IUS) - Tiled Large Element 1.75D Aperture with Dual Array Modules by Adjacent Integration of PIN-PMN-PT Transducers and Custom High Voltage Switching ASICs
摘要： A technique is described, to efficiently evaluate the reliability of an RF semiconductor device when several different mechanisms contribute simultaneously to its wearout. This is of interest for present-day GaN HEMT devices because symptoms of several simultaneous degradation mechanisms have been reported widely. The technique involves first finding DC parameters that are “signatures” of each mechanism. Then, separate DC-stress lifetests are performed to find the degradation rates for the signature parameters, at several temperatures, and the corresponding Arrhenius curves. Next, an RF-stress lifetest (with only one stress condition) is performed, while monitoring all of the signature parameters and the RF performance. This is utilized to determine the “scaling factors” between the rates of change in the DC lifetests and the rates of change in the RF application. Applying these scaling factors to the original Arrhenius curves gives an “overall” Arrhenius plot for the RF application with several different lines, for the different degradation mechanisms. The technique can be extended to further degradation mechanisms, by conducting further DC and RF lifetests while monitoring appropriate signature parameters.
关键词： lifetesting,semiconductor device reliability,gallium nitride,Failure analysis,HEMTs
更新于2025-09-23 15:19:57