Simulation of Normally-Off Vertical GaN MOSFET with a Novel Enhanced Sidewall Channel by Selective Area Growth

In the present study, a novel normally-off vertical GaN MOSFET with an enhanced AlGaN/GaN channel on the sidewall has been proposed using the technology computer-aided design (TCAD) simulation. By using the selective area growth process, the trench structure and the enhanced sidewall channel are formed simultaneously, which is beneficial to enhance the conduction capability compared with the conventional trenched MOSFET. It demonstrates that a proper hole concentration and thickness of the p-GaN layer are key parameters to balance the threshold voltage, on-state resistance, and off-state breakdown voltage, resulting in the highest Baliga's figure of merit value. Furthermore, a p-GaN shield layer is also adopted as a junction termination extension to modulate the electric field around the trench bottom. By optimizing the device parameters, a normally-off GaN MOSFET with good performance is designed.