Modeling of internal quantum efficiency in micro-LEDs with surface nonradiative recombination

InGaN-based blue micro-scale light-emitting diodes (micro-LEDs) experience a significant reduction in external quantum efficiency (EQE) as their chip size decreases. In contrast, InGaN red micro-LEDs maintain a relatively stable EQE, regardless of chip size. To understand these size-dependent efficiency characteristics for both blue and red InGaN micro-LEDs, we have developed a comprehensive model of internal quantum efficiency (IQE) including both the effects of surface recombination velocity (SRV) and diffusion length. For micro-LEDs with relatively long diffusion lengths of exceeding 1 μm, IQE decreases significantly as chip size decreases or SRV increases. In contrast, for micro-LEDs with short diffusion lengths of less than 0.1 μm, which applies to InGaN red LEDs, IQE changes only slightly with reductions in chip size or increases in SRV. Our developed IQE model is expected to provide valuable insights into the efficiency characteristics of micro-LEDs, contributing to improved efficiency.