高场应力及栅应力下AlGaN/GaN HEMT器件退化研究

采用不同的高场应力和栅应力对AlGaN/GaN HEMT器件进行直流应力测试，实验发现：应力后器件主要参数如饱和漏电流，跨导峰值和阈值电压等均发生了明显退化，而且这些退化还是可以完全恢复的；高场应力下，器件特性的退化随高场应力偏置电压的增加和应力时间的累积而增大；对于不同的栅应力，相对来说，脉冲栅应力和开态栅应力下器件特性的退化比关态栅应力下的退化大.对不同应力前后器件饱和漏电流，跨导峰值和阈值电压的分析表明，AlGaN势垒层陷阱俘获沟道热电子以及栅极电子在栅漏间电场的作用下填充虚栅中的表面态是这些不同应 关键词： AlGaN/GaN HEMT器件 表面态(虚栅) 势垒层陷阱 应力

Degradation under high-field stress and gate stress of AlGaN/GaN HEMTs

After subjecting to different high-field stress and gate stress，a recoverable degradation has been found，consisting of the decrease of saturation drain current I_Dsat and maximal transconductance g_m，and the positive shift of threshold voltage V_TH. AlGaN/GaN HEMTs were degradated more with the high-field strss voltage and the stress time increasing. Relatively，under gate pulse stress and on-state gate stress，the degradation was more obvious than under off-state gate stress. By analyzing the shift of primary parameters，we found that the hot carriers generated by impact ionization and trapped by traps in AlGaN barrier layer，and the emission of electrons from gate electrode filling in surface states at high gate-to-drian electric fileds, were the primary reasons causing device degradation after different stress. Off-state stress，on-state stress and pulse-state stress measurements reveal that the passivation treatment just changes short-time current collapse into long-time degradation，which dose not solve the reliability problem of AlGaN/GaN.