Low Threshold Voltage Shift in AlGaN/GaN MIS-HEMTs on Si Substrate Using SiNx/SiON as Composite Gate Dielectric

Xiaodong Zhang,Baoshun Zhang,Hui Zhang,Yaming Fan,Zhihua Dong,Xing Wei,Peipei Zhang,Li Zhang,Guohao Yu,Yong Cai,Xuguang Deng,Kai Fu,Houqiang Fu

doi:10.3390/electronics11060895

Abstract

This study has demonstrated AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) on Si substrates with a SiNx/SiON composite gate dielectric. The threshold voltage shift in the devices was investigated. The MIS-HEMTs with the SiNx/SiON composite gate dielectric exhibited superior threshold voltage uniformity and small threshold voltage hysteresis than the reference device with SiNx only gate dielectric. The variation of the device threshold voltage was mainly related to trapping process by the interface states, as confirmed by band diagrams of MIS-HEMTs at different gate biases. Based on frequency-dependent capacitance measurements, interface state densities of the devices with the composite and single gate dielectrics were extracted, where the former showed much smaller interface state density. These results indicate that the SiNx/SiON composite gate dielectric can effectively improve the device performance of GaN-based MIS-HEMTs and contribute to the development of high-performance GaN electronic devices.

Highlights

Gallium nitride (GaN) based high electron mobility transistors (HEMTs) have been widely investigated for power electronics due to their high breakdown voltage, low on-state resistance, and high switching speed [1,2]
The existence of surface traps led to larger gate leakage current, lag of threshold voltage, breakdown voltage reduction, and other reliability issues in the HEMT devices [6,7]
In order to solve these issues induced by surface traps and improve the gate stability, an insulating dielectric material is usually inserted under the gate to form a metal-insulator-semiconductor HEMT

Summary

Introduction

Gallium nitride (GaN) based high electron mobility transistors (HEMTs) have been widely investigated for power electronics due to their high breakdown voltage, low on-state resistance, and high switching speed [1,2]. Heteroepitaxially grown HEMTs are prone to the formation of traps in the buffer layer, in the channel layer, and on the surface. The existence of surface traps led to larger gate leakage current, lag of threshold voltage, breakdown voltage reduction, and other reliability issues in the HEMT devices [6,7]. In order to solve these issues induced by surface traps and improve the gate stability, an insulating dielectric material is usually inserted under the gate to form a metal-insulator-semiconductor HEMT (MIS-HEMT). The introduction of an insulating gate dielectric can effectively reduce the gate leakage current, surface state density, and improve the overall performance of the devices [8–10]

Methods

Results

Conclusion