Generated Carrier Dynamics in V-Pit-Enhanced InGaN/GaN Light-Emitting Diode
Generated Carrier Dynamics in V-Pit-Enhanced InGaN/GaN Light-Emitting Diode
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DOI：
10.1021/acsphotonics.7b00944
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发表时间：
2018-03-01
期刊：
影响因子：
7
通讯作者：
Roqan, Iman S.
中科院分区：
文献类型：
--
作者：
Ajia, Idris A.;Edwards, Paul R.;Roqan, Iman S.
研究了V型凹坑对一种高内量子效率（IQE）> 80%的蓝色InGaN/GaN多量子阱（MQW）发光二极管（LED）光学特性的影响。LED的结构增强，通过将一个预MQW InGaN应变释放层与低InN含量和图案化的蓝宝石衬底。为了进行比较，对在类似条件下生长的常规（未增强的）InGaN/GaN MQW LED（具有46%的IQE）进行相同的测量。扫描透射电子显微镜揭示了在未增强的LED中不存在V-坑，而在增强的LED中，具有{10-11}面的V-坑，从穿透位错（TD）出现，是突出的。阴极射线发光映射揭示了V-坑附近的发光特性，表明V-坑缺陷的形成可以促进TD缺陷态周围的缺陷中和势垒的生长。TDs在多量子阱中的贡献减少，使得富含铟的定位位点可以作为有效的重组中心。光致发光和时间分辨光谱测量表明，V-坑在产生的载流子速率和下垂机制中起着重要作用，表明量子限制斯塔克效应在低产生的载流子密度下被抑制，之后载流子动力学和下垂由载流子溢出效应控制。
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.