摘要:
InGaN/GaN基阱垒结构LED当注入的电流密度较大时, LED的量子效率随注入电流密度增大而下降, 即droop效应.本文在Si （111）衬底上生长了 InGaN/GaN 基蓝光多量子阱结构的LED,通过将实验测量的光电性能曲线与利用ABC模型模拟的结果进行对比, 探讨了droop效应的成因.结果显示：温度下降会阻碍电流扩展和降低空穴浓度, 电子在阱中分布会越来越不平衡,阱中局部区域中因填充了势能越来越高的电子而溢出阱外, 从而使droop效应随着温度的降低在更小的电流密度下出现且更为严重, 不同温度下实验值与俄歇复合模型模拟的结果在高注入时趋势相反.这此结果表明,引起 droop效应的主因不是俄歇非辐射复合而是电子溢出,电子溢出的本质原因是载流子在阱中分布不均衡.
Abstract:
InGaN/GaN based light emitting diodes （LEDs） suffer from decrease in efficiency at a high injection current level which is called efficiency droop. In this paper, blue InGaN/GaN multiple quantum well light emitting diodes on Si （111） substrates are prepared, and their electroluminescence spectra are tested. Comparing the experimental measurements with the simulating results based on simple ABC model, the cause for quantum efficiency droop is investigated. The results show that the light emitting diode has worse electron spreading and less hole concentration with temperature decreasing, and the electrons will overflow frome the well after filled up in higher and higher state for their inhomogeneous distribution, thus efficiency droop will happen at a lower injection more severely for electron leakage under lower injection, and experimental measurements are in disagreement with simulation results of Auger recombination at high injection current levels under different temperatures. The results confirm that the main factor for efficiency droop is not Auger nonradiative recombination but electron leakage, and the essential cause for electron leakage is severe carrier localization.
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