由于高的表面体积比,基于InGaN的微发光二极管(μLED)强烈地遭受由侧壁缺陷引起的表面复合。此外,随着芯片尺寸的减小,电流扩散将相应增强,这因此进一步限制了载流子注入和外部量子效率(EQE)。在这项工作中,我们建议通过控制电流扩散效应来降低侧壁缺陷处的非辐射复合率。为此,我们通过减小量子势垒厚度来适当地降低垂直电阻率,从而使电流较少地水平扩散到侧壁缺陷。因此,以表面非辐射复合的方式消耗的载流子少得多。我们的计算结果表明,抑制表面非辐射复合可以更好地促进空穴注入效率。我们还制造了生长在Si衬底上的μLED,测量结果与数值计算结果一致,这样,所提出的具有适当薄量子势垒的μLED的EQE可以增强,由于较小的电流扩散效应和减少的表面非辐射复合。
Owing to high surface-to-volume ratio, InGaN-based micro-light-emitting diodes (μLEDs) strongly suffer from surface recombination that is induced by sidewall defects. Moreover, as the chip size decreases, the current spreading will be correspondingly enhanced, which therefore further limits the carrier injection and the external quantum efficiency (EQE). In this work, we suggest reducing the nonradiative recombination rate at sidewall defects by managing the current spreading effect. For that purpose, we properly reduce the vertical resistivity by decreasing the quantum barrier thickness so that the current is less horizontally spreaded to sidewall defects. As a result, much fewer carriers are consumed in the way of surface nonradiative recombination. Our calculated results demonstrate that the suppressed surface nonradiative recombination can better favor the hole injection efficiency. We also fabricate the μLEDs that are grown on Si substrates, and the measured results are consistent with the numerical calculations, such that the EQE for the proposed μLEDs with properly thin quantum barriers can be enhanced, thanks to the less current spreading effect and the decreased surface nonradiative recombination.