Electrothermal coupling characteristics of GaN HEMTs

The electrothermal coupling effect of GaN HEMT under high power conditions is studied. By establishing the electrothermal coupling simulation model based on the Monte Carlo method, the microscopic thermal transport mechanism and its nonlinear coupling relationship with electron transport characteristics in GaN HEMT are systematically revealed. The effect of AlN interlayer thickness on 2DEG concentration distribution and interfacial thermal resistance is investigated. It is found that when the AlN interlayer thickness is 1 nm, the interfacial thermal boundary resistance can be effectively controlled to 25 m 2 ·K/GW while maintaining the significant increase of 2DEG concentration (1.2×10 3 cm 2 ). The numerical simulation results show that the predicted hot spot temperature (285 °C) is 15% lower than the measured value (327 °C) at Vd=20V due to neglecting the nonequilibrium phonon transport effect in the traditional Fourier heat transfer model. By means of multi-physical field coupling analysis, it is confirmed that there are significant nonlinear characteristics in the regulation of carrier transport characteristics by gate bias voltage: when Vg increases from -4 V to 0 V, the saturation current of the drain increases by 62.5%, but the electron mobility decreases by 19.4%. Meanwhile, the peak electric field intensity at the gate drain side increases by 50%, causing the electron temperature near the gate region to increase by 60 K. The threshold effect of AlN interlayer thickness on the thermoelectric properties is found, and the temperature rise rebound amplitude of 2 nm AlN layer devices is 3.6% due to the polarization charge attenuation and phonon scattering enhancement caused by lattice relaxation when the AlN interlayer thickness exceeds 1 nm. The electro-thermal co-optimization scheme proposed in this study provides an important theoretical basis for the structural design of high-reliability GaN power devices in 5G communication and power electronic systems.