凹槽栅增强型GaN功率器件的开关特性研究

Switching Performance Evaluation of Recessed-gate E-mode GaN MOS-HEMT

由于AlGaN/GaN异质结界面自发极化和压电极化产生的二维电子气,使器件处于常开状态,需要施加额外的负栅极电压将其关断。而增强型p-GaN栅结构的肖特基栅漏电大,极大地限制了器件的工作电压范围。本文基于原子层刻蚀及原子层沉积技术,在硅基衬底上制备出凹槽栅增强型GaN MOS-HEMT功率器件,阈值电压为2.5 V,电流开关比>1010,衬底接地时击穿电压为760 V。基于Silvaco TCAD建立了电学输运模型,对器件的转移输出特性进行拟合,并提取模型参数。同时,基于器件-电路混合电路仿真器MixedMode建立双脉冲测试电路,首次评估了凹槽栅增强型GaN MOS-HEMT器件的开关特性。当负载电流为12 A时,器件的导通上升时间为1 ns,关断下降时间为1.6 ns,处于现有文献报道的最低值。这些结果表明,凹槽栅增强型GaN MOS-HEMT在功率器件领域具有广阔的应用前景。

A two-dimensional electron gas is generated due to the spontaneous and piezoelectric polarization at the interface of the AlGaN/GaN heterojunction,causing the device to remain normally-on and requiring an additional negative gate voltage to be applied to turn it off.Moreover,the high Schottky gate leakage current of the enhancement mode(E-mode)p-GaN gate structure greatly limits the device's operating voltage range.In this work,recessed-gate E-mode GaN MOS-HEMTs have been fabricated using atomic layer etching and deposition technology,resulting in a threshold voltage of 2.5 V,a current on/off ratio of>1010,and a grounded substrate breakdown voltage of 760 V.An electrical transport model of the device has been established using Silvaco TCAD to fit its transfer and output characteristics and extract model parameters.Meanwhile,a double-pulse test circuit has been established using the MixedMode simulator to evaluate the switching characteristics of the recessed-gate E-mode GaN MOS-HEMT device for the first time.With a load current of 12 A,the device was demonstrated to have a turn-on time of 1 ns and a turn-off time of 1.6 ns,which represent the lowest reported values achieved in GaN devices to date.These results indicate that the recessed-gate E-mode GaN MOS-HEMT has broad application prospects in the field of power devices.