Study of AlGaN/GaN Vertical Superjunction HEMT for Improvement of Breakdown Voltage and Specific On-Resistance

Miao Zhang,Fan Xia,Xiaoyu Xia,Yong Huang,Yuan Li,Xiuyang Tan,Zhiyou Guo,Jiancheng Ma,Huiqing Sun

doi:10.1109/access.2021.3049374

Abstract

A GaN-based vertical superjunction high electron mobility transistor (SJ HEMT) with a composite structure (CS-SJ HEMT) is proposed and analyzed by Silvaco TCAD to improve the breakdown voltage and specific on-resistance (R onA ). In this paper, CS-SJ HEMT is compared with SJ HEMT with traditional structure (TS-SJ HEMT), SJ HEMT with only particular doping pillars (DP-SJ HEMT) and SJ HEMT with only special P-gate (SP-SJ HEMT). The particular doping pillars mean the doping concentration of n-pillar increases with a gradient from top to bottom, and the concentration of p-pillar is the same as the middle of n-pillar, which reduces the R onA by only 4%. The special P-GaN cap layer can reduce the R onA by 10%, and it can even increase the on-state current in the saturation region. The CS-SJ HEMT combines both doping pillars and special P-gate structures, and the R onA can be reduced by 14%. By the optimized design, the R onA can be reduced by 30% with BV = 2580 V, or the R onA can be reduced by 21% with BV = 2720 V. These results show that the composite structure of SJ HEMT contributes to improving the BV and R onA and propose a useful approach for improving the vertical HEMTs.

Highlights

As a representative of the III-nitride material, GaN has a wide band, high electron saturation drift velocity, high electron mobility, high critical field strength, high thermal conductivity and other excellent physical properties, so it has become an ideal power electronic material [1]–[5]
The introduction of structures such as P-buried layer [13], superjunction (SJ) [14]–[17] and current barrier layer (CBL) of SiO2 material [18] has promoted the improvement of vertical device performance and laid the foundation for the current demand for a wider range of applications
When T3 = 3μm and T1(T5) = 2.5μm, the breakdown voltage (BV) can increase to 2720 V, and RonA can decrease to 3.18 m ·cm2, which means it is reduced by 21%; when T3 = 8μm and T1(T5) = 0.6μm, the BV can increase to 2580 V, and RonA can decrease to 2.80 m ·cm2, which means it is reduced by 30%

Summary

INTRODUCTION

As a representative of the III-nitride material, GaN has a wide band, high electron saturation drift velocity, high electron mobility, high critical field strength, high thermal conductivity and other excellent physical properties, so it has become an ideal power electronic material [1]–[5]. Compared with traditional Si materials, power-switching devices based on GaN power electronic materials have higher power density output and energy conversion efficiency. They can make the system smaller and lighter, effectively reducing the size and weight of power electronic devices [6]–[9], greatly reducing system fabrication and production costs. Vertical GaN-based HEMT devices [10]–[12] have attracted much attention in the field of high-power electronics with their excellent performance. Two-dimensional device simulation using Silvaco-TCAD software reveals its intrinsic operation mechanism by exploiting the potential distribution, electric field distribution and current density distribution These results have important implications for the optimization and design of GaN-based vertical HEMTs

DEVICE STRUCTURES AND PARAMETERS

FABRICATION PROCESS

Findings

CONCLUSION