GaN基发光二极管寿命测试及失效分析

Life Tests and Failure Analysis of GaN-based LEDs

将来自相同外延片和相同制作工艺的30只GaN基绿色发光二极管管芯分成3组,分别加30、40和60 mA电流进行不同时间的老化试验。在老化之前和老化期间测量了器件的光输出功率和I-V特性。将测得的光输出功率数据对时间进行指数函数拟合,得到了每一组器件的退化率及寿命,并推出器件在正常使用条件下的寿命。实验数据分析表明在电流应力作用下,GaN基绿色发光二极管的正向电压随着老化时间的增加单调上升,同时光功率下降。在60 mA下老化的管芯的串联电阻退化严重。对失效器件进行了失效机理分析。

Three groups of GaN-based green LED chips which were taken from the same expitaxy and were made with the same manufacturing processes have been biased at different DC forward currents. 30 mA, 40 mA, 60 mA at room temperature for different time. The optical properties and Ⅰ-Ⅴ characteristic of these chips were measured before and during the aging test. The data of light output power were fitted as exponential function on the time index and the degradation rates of every group chips were obtained, and then the life time of every group chips using under normal conditions was extrapolated. Test data analysis showed that the forward voltage of the GaN-based chips aged under electric stress increased monotonously with time meanwhile the light output power decreased. The series resistance of chips aged under 60 mA DC current degraded badly. And failure mechanism for the failure chips was analyzed.