针对GaN基蓝光Micro-LED芯片,采用温度应力和电压应力的实验方法研究了其反向漏电流失效机理.结果表明,在温度应力下,Micro-LED芯片退化前的反向漏电流主要由多步热辅助隧穿电流构成,且受Poole-Frenkel(PF)隧穿机制影响;电压应力(-85 V)退化后,反向漏电流会随着应力时间的延长而增大,此时由多步热辅助隧穿电流转换为空间电荷限制电流机制(SCLC).通过分析退化前后的能带图得知,长时间的电压应力会发生击穿现象,导致Micro-LED芯片内部电场剧烈变化,电子能够以高能量碰撞到晶格原子,产生大量的载流子,从而增加了非辐射复合率,使得反向漏电流由原来的1.9766×10-7 A增大到1.5834×10-4 A.
Analysis of Failure Mechanism of Reverse Leakage Current in GaN-based Micro-LEDs
For GaN-based blue Micro-LED chips,experimental methods involving temperature and voltage were used to investigate the reverse leakage current failure mechanism in this paper.The results demonstate that,under temperature stress,the reverse leakage current of Micro-LED chips,prior to degradation,is primarily composed of multi-step thermal-assisted tunneling current,which is significantly influenced by the Poole-Frenkel(PF)tunneling mechanism.After degradation under voltage stress(-85 V),the reverse leakage current increases with the extension of stress time,transitioning from a multi-step thermal-assisted tunneling current to a space-charge-limited current(SCLC).Through analyzing the band diagrams before and after degradation,it was determined that prolonged volt-age stress leads to breakdown phenomenon,resulting a drastic change in the internal electric field of the Micro-LED chip.Electrons are then able to collide with lattice atoms with high energy,generating numerous carriers.Conse-quently,this increase the rate of non-radiative recombination,causing the reverse leakage current to increase from an original value of 1.9766×10-7 A to 1.5834×10-4 A.
Micro-LEDfailure mechanismnon-radiative recombinationtrap-assisted tunnelingreverse leakage current
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