Impacts of removing the p-AlGaN electron blocking layer for ultra-low-current injected blue micro-LEDs

In this work, the 34 × 58 μm² ultra-low-current injected blue micro-LEDs with and without p-AlGaN electron blocking layer (EBL) were fabricated. The measured optoelectronic performance of these micro-LEDs reveals that the peak external quantum efficiency (EQE) could be enhanced by 5.5% (from 32.8% to 34.6%) at the current density of 0.4 A/cm² by removing the EBL. The results of secondary ion mass spectrometry and Raman measurement indicated that there would be more Mg content in the p-region and less compressive stress in multiple quantum-wells of micro-LEDs by removing p-AlGaN EBL. In addition, the carrier transportation and recombination mechanisms in these micro-LEDs were analyzed by using the cryogenic temperature experiment, and the micro-hyperspectral imaging measurement showed that the difference in Mg content also affected the current spreading effect in these micro-LEDs. Finally, the results of junction temperature and surface temperature distribution indicate that removing EBL could enhance the thermal performance of ultra-low-current injected micro-LEDs. These results may give a reference for the development of wearable and near-to-eye displays.