Edge Termination for III-Nitride Vertical Power Devices Using Polarization Engineering

A method for edge termination utilizing polarization-induced charge for GaN vertical power devices is presented. The polarization edge termination is simulated on a GaN power diode and consists of a 5-nm-thick n-type AlGaN layer on top of a p-type GaN layer that is located at the periphery of the main p-n junction. The spontaneous and piezoelectric polarization present in III-nitrides result in fixed charges at the AlGaN/GaN heterointerface, and the p-GaN layer becomes depleted at this interface under reverse bias. Numerical simulations show that this AlGaN/GaN heterointerface can be engineered to control the depletion region under reverse bias to prevent localization of electric fields and premature avalanche breakdown. Nearly parallel-plate reverse breakdown performance can be achieved. In addition, a simple analytical model based on charge balancing predicts the performance of this edge termination method.