We investigate the effects of V-pits on the optical properties of a state-of-the-art, highly efficient, blue InGaN/GaN multi-quantum-well (MQW) light-emitting diode (LED) with a high internal quantum efficiency (IQE) of >80%. The LED is structurally enhanced by incorporating a pre-MQW InGaN strain-relief layer with low InN content and a patterned sapphire substrate. For comparison, a conventional (unenhanced) InGaN/GaN MQW LED (with an IQE of 46%) grown under similar conditions was subjected to the same measurements. Scanning transmission electron microscopy reveals the absence of V-pits in the unenhanced LED, whereas in the enhanced LED, V-pits with {10-11} facets, emerging from threading dislocations (TDs), were prominent. Cathodoluminescence mapping reveals the luminescence properties near the V-pits, showing that the formation of V-pit defects can encourage the growth of defect-neutralizing barriers around TD defect states. The diminished contribution of TDs in the MQWs allows indium-rich localization sites to act as efficient recombination centers. Photoluminescence and time-resolved spectroscopy measurements suggest that the V-pits play a significant role in the generated carrier rate and droop mechanism, showing that the quantum-confined Stark effect is suppressed at low generated carrier density, after which the carrier dynamics and droop are governed by the carrier overflow effect.

中文翻译：

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V坑增强的InGaN / GaN发光二极管中产生的载流子动力学

我们研究了V凹坑对具有高内部量子效率的最新，高效，蓝色InGaN / GaN多量子阱（MQW）发光二极管（LED）的光学特性的影响（IQE）> 80％。通过合并具有低InN含量的预MQW InGaN应变消除层和带图案的蓝宝石衬底，可以在结构上增强LED。为了进行比较，对在相似条件下生长的常规（增强型）InGaN / GaN MQW LED（IQE为46％）进行了相同的测量。扫描透射电子显微镜显示在未增强的LED中不存在V形凹坑，而在增强型LED中，由螺纹位错（TD）出现的具有{10-11}刻面的V形凹坑是突出的。阴极发光映射揭示了V形凹坑附近的发光特性，表明形成V坑缺陷可以促进TD缺陷状态周围缺陷中和势垒的生长。量子阱中TD的贡献减少，使得富含铟的定位位点可以充当有效的重组中心。光致发光和时间分辨光谱测量表明，V坑在生成的载流子速率和下垂机理中起着重要作用，表明在低生成的载流子密度下，量子限制的斯塔克效应受到抑制，此后载流子动力学和下垂被抑制。由载波溢出效应决定。