Enhanced size-dependent efficiency of InGaN/AlGaN near-ultraviolet micro-LEDs

Abstract

This study presents an approach for enhancing the external quantum efficiency (EQE) of multiple-quantum-well InGaN/AlGaN near-ultraviolet (NUV) micro-light-emitting diodes (micro-LEDs) without changing the epitaxial layer. Unlike the size-dependent EQE reduction observed in blue, green, and red micro-LEDs, the EQE of NUV micro-LEDs at high current densities (≥10 A/cm2) improves as the device dimensions shrink from 500 × 500 μm2 to 20 × 20 μm2. A 20 × 20 μm2 micro-LED achieves a peak EQE of 12.3%, compared to 8.60% for a larger 500 × 500 μm2 micro-LED. Experimental results attribute this EQE enhancement to improved light-extraction efficiency, driven by better current spreading. In larger micro-LEDs, pronounced current crowding causes carrier overflow from the active region, leading to reduced EQE at high current densities. These findings highlight the promising potential of NUV micro-LEDs for diverse applications.