氮化镓基高电子迁移率晶体管Kink效应研究

Study on Kink Effect in GaN-Based High Electron Mobility Transistor

研究了氮化镓(GaN)基高电子迁移率晶体管(HEMT)发生Kink效应的物理机制,并进行了实验测试。测试结果表明,当第一次扫描、漏极电压较大时,扩散进入耗尽区的电子在高场作用下形成热电子,碰撞电离出深能级施主态中的非平衡电子,第二次扫描的Kink效应减弱。当第一次扫描、漏极电压较小时,扩散进入耗尽区的电子被浅能级缺陷态捕获,第二次扫描的Kink效应增强。在开态下,增大反向栅极电压,可减小沟道电子浓度,进而减小电子捕获效应,Kink效应减弱。在半开态和闭态下,Kink效应不显著。最终得出,GaN缓冲层内类施主型缺陷态对沟道电子的捕获和热电子辅助去捕获,是Kink效应发生的主要原因。

The physical mechanism of well-known kink effect in GaN-based high electron mobility transistors(HEMT)was studied,and relative experiments was carried out.The experimental results showed that,when the first scan drain voltage was relatively large,many electrons diffusing into the depletion region could become high-energetic hot electrons due to the high electrical field,and then the nonequilibrium electrons trapped at the deep donors were released by impact ionization,giving rise to an improved kink effect at second scan.When the first scan drain voltage was low,the donor states inside the depletion region would significantly capture the electrons from 2DEG,leading to a deteriorative kink effect at second scan.Under the on state,increasing the reverse gate voltage could decrease the 2EDG density in the channel,and weaken the trapping effect and thus the kink effect.Under the semi-on and off states,the trapping effect induced by the gate leakage current was not important.Based on the above results,it was believed that the trapped electrons and hot electrons assist detrapped electrons effect occurred in the GaN buffer layer were majorly responsible for the kink effect occurred in GaN-based HEMTs.