Advances of beveled mesas for GaN-based trench Schottky barrier diodes

Fuping Huang,Qing Li,Xingyu Jia,Zi-Hui Zhang,Zhen Xin,Yonghui Zhang,Yajin Liu,Chunshuang Chu,Quan Zheng,Kangkai Tian

doi:10.1063/5.0033844

Abstract

In this article, we propose and investigate a GaN-based trench metal–insulator–semiconductor barrier Schottky rectifier with a beveled mesa and field plate (BM-TMBS). According to our study, the beveled mesa and field plate structures help to reduce the density of potential lines at the mesa corner and deplete the drift region in two-dimensional mode, respectively. By doing so, the electric field at the bottom corner of the trenches and Schottky contact/GaN interface can be decreased significantly and the breakdown voltage can also be improved remarkably when compared with the conventional TMBS rectifiers and the planar Schottky barrier diodes. Meanwhile, assisted by the beveled mesa structure, the improved current spreading effect and a better conductivity modulation can be obtained in the forward-conduction state. Our studies also show that the electric field profiles and charge-coupling effect can be influenced by the mesa angle, the insulating layer thickness (Tox), and the trench depth (Dtr). As a result, the optimized BM-TMBS rectifiers can obtain a high BV of ∼2 kV and a current density of ∼3 kA/cm2 at the forward bias of 2 V.

Highlights

Silicon-based power devices have reached their theoretical limits in terms of chip size and physical properties
The BM-trench metal–insulator–semiconductor (MIS) barrier Schottky (TMBS) rectifier can effectively suppress the electric field at the mesa corners, which is very helpful to further enhance the breakdown voltage
Our studies show that the breakdown voltage can be remarkably enhanced by combining the beveled mesa and the field plate

Summary

INTRODUCTION

Silicon-based power devices have reached their theoretical limits in terms of chip size and physical properties. According to our previous report, the GaN-based TMBS structure has been designed, and the effect of various parameters on the breakdown voltage and leakage current has been analyzed in detail, e.g., the mesa width, the insulating layer thickness, and the trench depth.. A vertical Ga2O3 Schottky barrier diode with small-angle beveled field plates has been reported recently, and it shows a breakdown voltage of 1.1 kV with a bevel angle of ∼1○. In this work, we take beveled GaN-based TMBS rectifiers as an example to conduct an in-depth study on the design principles for such devices, and we believe that the reported device physics can be applied to beveled Ga2O3 Schottky barrier diodes. We conduct an in-depth study on device physics, and a systematic optimization strategy for the GaN-based BM-TMBS rectifiers is reported in this work

DEVICE STRUCTURES AND NUMERICAL PARAMETERS

RESULTS AND DISCUSSION

Impact of the trench depths for BM-TMBS rectifiers

Forward characteristics for the optimized GaN-based BM-TMBS rectifiers

CONCLUSION