中文摘要：

对小功率白光GaN基发光二极管（LED）在室温、40℃和70℃下进行温度加速老化寿命实验,通过对老化前后不同时间段器件的电学、光学和热学特性进行测量来分析器件的失效机理,着重分析器件的芯片和荧光粉的失效机理.器件老化前后的I-V特性表明：老化过程中,器件的串联电阻和低正向偏压下的隧道电流增大,这是由于器件工作时其芯片的欧姆接触退化和半导体材料的缺陷密度升高而引起的.器件的热特性表明：高温度应力下器件的热阻迅速变大,封装材料迅速退化,这是器件退化的主要原因;光谱曲线表明温度加速了器件的光功率衰减,并使荧光粉的转换效率迅速降低.最后使用阿伦尼斯方程对室温下器件的预测寿命进行了计算,并分析了GaN基白光LED的失效机理.

英文摘要：

Accelerated aging and life-time tests at ambient temperatures of 40 ℃,70 ℃ and room temperature were carried out on GaN-based white light-emitting diodes（LEDs）.The electrical,optical and thermal characteristics of the device were compared before and after different aging times in order to investigate the failure mechanism of the device.Here,we mainly analyzed the failure mechanism related with the chip and the phosphor of the LED.The current-voltage characteristics demonstrated that both the series resistance and the tunnel current increase under lower forward voltages after aging,which were due to the degradation of p-type ohmic contact and the increase of defect density.The thermal characteristics confirmed that the thermal resistance increased rapidly under high aging temperature.This was mainly attributed to the fracture of different materials inside the devices caused by the difference in thermal expansion coefficients.Optical measurements indicated that high aging temperature could accelerate the degradation of output power and reduce the conversion efficiency of the phosphor as well.Finally,the life time of the device was calculated using Arrhenius-equation,and the failure mechanism was analyzed.