Comprehensive Design and Numerical Study of GaN Vertical MPS Diodes Towards Alleviated Electric Field Crowding and Efficient Carrier Injection

Abstract

In this paper, we systematically investigated the impact of the key structural parameters on the reverse and forward characteristics of gallium nitride (GaN) based vertical merged pn-Schottky (MPS) diode by numerical simulation. In comparison with conventional GaN-based vertical Schottky barrier diode, the MPS structure can suppress the high electric field at the Schottky interface with the inserted p-GaN, thereby enhancing the reverse breakdown characteristics. However, the adoption of the p-GaN structure can result in a locally crowded electric field at reserve bias condition and thus a premature breakdown of the device. Moreover, the p-GaN structure depletes the vertical channel region, which may degrade the on-performance at forward bias condition. We found that the doping concentration, width, and depth of the p-GaN structure are closely correlated with the electric field distribution at reverse bias and the channel resistance at forward bias, and thus determines the reverse and forward characteristics of the MPS diodes. The unique forward unipolar/bipolar characteristics of the MPS diode was also investigated and discussed systematically. The results can pave the way for the development of GaN power electronic devices towards a compact high-frequency and high-voltage power electronic system.