Degradation by sidewall recombination centers in GaN blue micro-LEDs at diameters < 30 μm

A matrix of blue GaN/InGaN multi-quantum-well (MQW) micro-Light-Emitting Diodes (micro-LEDs) with diode dimensions ranging from 2 to 100 mu m was prepared by masked dry etching and characterized by Photoluminescence (PL), Microcathodoluminescence (MCL), capacitance-voltage profiling in the dark and under monochromatic illumination, current-voltage measurements, admittance spectra, Deep Level Transient Spectroscopy with electrical (DLTS) and optical (ODLTS) injection. The changes observed in the PL, MCL spectra are due to the formation of deep hole traps at E-v+ 0.75 eV and electron traps at E-c-1 eV in the sidewalls of the micro-LEDs. The former give rise to the red defect band peaked near 600 nm and contribute to the increase of tunneling and leakage current with decreasing the diode diameter. The latter are prominent centers of nonradiative recombination. (C) 2022 Elsevier B.V. All rights reserved.