Efficiency degradation induced by surface defects-assisted tunneling recombination in GaN/InGaN micro-light-emitting diodes

Two GaN/InGaN micro-light-emitting diodes (micro-LEDs) grown on the same substrate with mesa sizes of 20 mu m and 100 mu m are measured from 100K to 300K to investigate the role that surface defects play in device efficiency. The experimental results show that the surface defect-assisted tunneling process dominates the nonradiative recombination of GaN/InGaN micro-LEDs at 100K, while the surface defect-assisted Shockley-Read-Hall recombination becomes dominant at room temperature. The temperature- and voltage-dependent tunneling current for both devices is calculated, which shows that the surface defect-assisted tunneling process is one of the major nonradiative recombination mechanisms in GaN/InGaN micro-LEDs with smaller mesa sizes at room temperature. A few potential approaches are proposed to suppress this surface defect-assisted tunneling recombination. The revised external quantum efficiency model is proposed to include the tunneling recombination effect and study the efficiency performance of GaN/InGaN micro-LEDs.