基于EMMI定位的GaN HEMT耐正向可靠性研究

Investigation of GaN HEMT Reliability Under Forward Gate Bias by Emission Microscope

GaN HEMT器件在高温栅偏压(HTGB)应力下会出现势垒退化现象,并进一步引发器件在射频工作下的不稳定和失效问题。使用微光显微镜(EMMI)作为主要工具,对器件的HTGB退化问题进行了研究。讨论了不同电偏置条件下器件EMMI发光的分布和形成机理,并对比了器件在HTGB试验前后EMMI发光图像的变化。HTGB后器件在反偏电场下出现明显新增EMMI亮点,对亮点的微区分析定位到栅下有外延位错对应的局部烧毁点。研究表明,延伸至栅下的外延位错会构成漏电通道,对HTGB下的退化和失效存在贡献。

Barrier degradation occurs in GaN HEMT devices under high temperature gate bias(HTGB)test,and further causes instability and failure problems during RF operation.In this paper,Emission Microscope(EMMI)was used as main tool to study the HTGB degradation of devices.EMMI luminescence distributions and formation mechanisms under varying external electrical bias conditions were discussed,and the EMMI luminescence differences of devices before and after HTGB stress were compared.New obvious EMMI spots under reversed electric field were found in devices after HTGB stress,and local burn point corresponding to the epitaxial dislocation under the gate was located in the bright spot area by micro analysis.This work shows that the epitaxial dislocations extended to gate may form leakage path,which contributes to the degradation and failure in HTGB stress.