Influence of AlN passivation on thermal performance of AlGaN/GaN high-electron mobility transistors on sapphire substrate: A simulation study

This work describes the self-heating effects on the behavior of AlGaN/GaN-based high-electron Mobility Transistors (HEMTs), which are grownon Sapphire substrate, using electro-thermal TCAD simulations. The proposed device, passivated with AlN/SiN, demonstrates more excellent thermal performance than the conventional one with SiN passivation due to the introduction of additional AlN on top of the device, which acts as a heat spreader. The electro-thermal simulations have carried out for different AlN thicknesses (0 mu m to 25 mu m), and the device with 5 mu m AlN shows better performance compared to others. The proposed AlN/SiN stacked passivation HEMT shows a comparatively small lattice temperature of 418 K, whereas the conventional HEMT with SiN passivation shows 578 K. All the devices (gate length, L-G = 1 mu m) switch from OFF-to ON-states using the voltage, V-GS from -10 V to 0 V with fixed bias, V-DS = 5 V. The values of saturation drain current density (I-DSS) and trans conductance (g(m)) are 0.7 A/mm and 173 mS/mm for the proposed HEMT with 5 mu m AlN considering the thermal simulation model. In contrast, the conventional device demonstrates those of 0.42 A/mm and 109 mS/mm, respectively. The similar to 0.32 A/mm of drain current recover for the proposed device with 5 mu m AlN from a conventional device because of the reduction of self-heating effects. Our study reveals that the AlN/SiN passivation HEMTs are a promising technology for high-power switching and microwave applications without significant reduction in device performance at high drain bias.