In this work, the size-dependent effect for InGaN/GaN-based blue micro-light emitting diodes (µLEDs) is numerically investigated. Our results show that the external quantum efficiency (EQE) and the optical power density drop drastically as the device size decreases when sidewall defects are induced. The observations are owing to the higher surface-to-volume ratio for small µLEDs, which makes the Shockley-Read-Hall (SRH) non-radiative recombination at the sidewall defects not negligible. The sidewall defects also severely affect the injection capability for electrons and holes, such that the electrons and holes are captured by sidewall defects for the SRH recombination. Thus, the poor carrier injection shall be deemed as a challenge for achieving high-brightness µLEDs. Our studies also indicate that the sidewall defects form current leakage channels, and this is reflected by the current density-voltage characteristics. However, the improved current spreading effect can be obtained when the chip size decreases. The better current spreading effect takes account for the reduced forward voltage.

中文翻译：

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表面复合对InGaN / GaN基蓝色微发光二极管的影响

在这项工作中，对InGaN / GaN基蓝色微发光二极管（µLED）的尺寸依赖性效应进行了数值研究。我们的结果表明，当诱发侧壁缺陷时，随着器件尺寸的减小，外部量子效率（EQE）和光功率密度急剧下降。观察到的结果是由于小型µLED的表面体积比更高，这使得侧壁缺陷处的Shockley-Read-Hall（SRH）非辐射复合变得不可忽略。侧壁缺陷还严重影响了电子和空穴的注入能力，使得电子和空穴被侧壁缺陷捕获以用于SRH重组。因此，不良的载流子注入将被视为实现高亮度µLED的挑战。我们的研究还表明，侧壁缺陷形成了电流泄漏通道，这反映在电流密度-电压特性上。然而，当芯片尺寸减小时，可以获得改善的电流扩展效果。更好的电流扩展效果考虑了降低的正向电压。