Design and TCAD Simulation of a Surface Super-Junction Based GaN HEMT with Enhanced Breakdown Voltage

A surface super-junction effect based AlGaN/GaN-on-Sapphire HEMT is discussed. The structure featuring an ohmic contacted p-GaN gate region extending to the drain area is called a p-string (PST), which is capable of regulating the off-state channel electric field. The impact of doping concentration and length of PST is thoroughly discussed. Additionally, the dynamic depletion and injection behavior of holes in PST are firstly demonstrated in GaN-based power devices. PST acts as a self-adjusting gate at the on-state, thus avoiding deteriorating conduction characteristics of the device. Through TCAD simulation, a blocking voltage (BV) of 930 V under $\mathrm{L}_\text{GD}= 7 \mu \mathrm{m}$ is achieved, enhanced by about 7 times compared with traditional-HEMT. While the device possesses $\mathrm{R}_{\text{on}}=10.2$ mΩ. mm and $\mathrm{I}_{\text{sat}}-208 \ \text{mA}/\text{mm}$ at $\mathrm{V}_\text{GS} =5$ V remaining unaffected. The dynamic turning-on time of ~20 ns is also obtained.