氮化镓基交流LED在交流应力下的老化机理研究

AC-LED is a prospective research field for GaN-based LED application,but there are some serious problems in ACLED,such as low chip area utilization rate and short lifetime.However,few researches were conducted on degradation mechanism of ACLED.In this proposal, degradation mechanism of GaN-based LED under AC stress is studied. Firstly, we investigate generation, development and movement of carriers and defects in GaN-based HV-LED under alternating electrical field ,and find out difference of degradation process in HV-LED between under alternating voltage stress and under constant equivelent voltage.Subsequently,we will reseach on luminescence mechanism and failure mode of Wheatstone-bridge ACLED under AC power,to analyze effect of epilayer structure,chip process and circuit structure on failure mode.Finally,through optimizing epitaxy process,chip process and number of micro-LEDs in rectify branches of WB-ACLED, WB-ACLED chip with longer lifetime comparable to that of DC-LED and chip area utilization rate more than 80% will be manufactured. After research on failure mode of ACLED，degradation testing method and criteria for evaluation of failure of ACLED will be established.

AC-LED是GaN基LED很有应用前景的一个研究方向，但是AC-LED面临芯片利用率低且易失效的问题，然而目前对于LED在交流电压应力失效机理的研究几乎是空白。本项目研究在交流应力下GaN基LED的失效机理。首先，在高压LED（HV-LED）基础上研究GaN基LED中载流子和缺陷在交变电场的产生、扩展和运动机制，对比研究HV-LED在交变电压下与恒定等效电压下的失效机理的差异；研究惠斯通桥路交流LED（WB-ACLED）在交流下的发光机理和失效原因，找出WB-ACLED失效与其外延结构、芯片工艺和电路结构的关系；最后，通过研究外延生长条件、优化芯片制造工艺和结构设计以及WB-ACLED整流支路和负载支路上微LED数量的最佳比例，研制芯片利用率在80%以上和寿命接近DC-LED寿命的WB-ACLED芯片。此外，通过研究AC-LED的失效机理，建立AC-LED的老化测试方法和失效评价标准。

本项目研究在交流应力下GaN基LED的失效机理。分析了交流驱动频率对AC-LED特性的影响，AC-LED在市电频率（50-60Hz）交流驱动下的老化机理，建立AC-LED失效的微观机制；开展AC-LED芯片设计和工艺研究，通过优化外延及工艺研制出芯片利用率在80%以上、寿命接近DC-LED寿命、光效120lm/W以上的AC-LED芯片；通过研究AC-LED的失效机理，建立AC-LED的老化测试方法和失效评价标准。项目发表文章2篇，申请专利3项，培养研究生2名。