半开态直流应力作用下AlGaN/GaN高电子迁移率晶体管的失效机制分析

本文研究了半开态直流应力条件下，AlGaN/GaN高电子迁移率晶体管的退化机制。应力实验后，器件的阈值电压电压正漂，栅漏串联电阻增大。利用数据拟合发现，沟道电流的退化量与阈值电压及栅漏串联电阻的变化量之间有密切的关系。分析表明，阈值电压的退化是引起饱和区沟道电流下降的主要因素，对于线性区电流，在应力开始的初始阶段，栅漏串联电阻的增大导致线性区电流的退化，随后沟道电流退化主要由阈值电压的退化引起。分析表明，在半开态应力作用下，栅泄露电流及热电子效应使得电子进入AlGaN层，被缺陷俘获，进而导致沟道电流退化。其中反向栅泄露电流中的电子被栅电极下AlGaN层内的缺陷俘获，导致阈值电压正漂；而热电子效应则使得栅漏串联区电阻增大。

Analysis of AlGaN/GaN high electron mobility transistors failure mechanism under semi-on DC stress

Semi-on DC stress experiments were conducted on AlGaN/GaN high electron mobility transistors (HEMTs) to find the degradation mechanisms during stress. A positive shift in threshold voltage (V_T) and an increase in drain series resistance (R_D) were observed after semi-on DC stress on the tested HEMTs. It was found that there exists a close correlation between the degree of drain current degradation and the variation in V_T and R_D. Our analysis shows that the variation in V_T is the main factor leading to the degradation of saturation drain current (I_DS), while the increase in R_D results in the initial degradation of I_DS in linear region in the initial several hours stress time and then the degradation of V_T plays more important role. Based on brief analysis, the electron trapping effect induced by gate leakage and the hot electron effect are ascribed to the degradation of drain current during semi-on DC stress. We suggest that electrons in the gate current captured by the traps in the AlGaN layer under the gate metal result in the positive shift in V_T and the trapping effect in the gate-drain access region induced by the hot electron effect accounts for the increase in R_D.