Cryogenic Insights into Bulk and Sidewall Nonradiative Recombination in AlGaInP Red Micro-LEDs

This study systematically investigates the temperature-dependent electrical and optical characteristics of AlGaInP-based red micro-light-emitting diodes (micro-LEDs) across a cryogenic range from 80 to 300 K. Experimental results demonstrate that decreasing temperatures lead to an increase in operating bias voltage and an enhancement in external quantum efficiency (EQE). Using a modified ABC model that incorporates carrier transport and leakage effects, the carrier recombination behaviors behind EQE results were analyzed. By fitting the size-dependent Shockley–Read–Hall (SRH) coefficients, the surface recombination velocity (SRV) was extracted, showing a reduction from 1. 53 × 105 cm/s at 300 K to 2. 62 × 104 cm/s at 80 K. Furthermore, an effective trap offset regarding the bulk defect (ΔE = 6. 05 meV) was identified through a theoretical fitting of the temperature-dependent bulk SRH lifetime. These findings provide a comprehensive understanding of the underlying thermal behavior of defects, specifically how bulk and surface SRH recombination evolve at cryogenic temperatures.