Quantitative evaluation of sidewall impact in micro-LEDs by ultrafast-gated hyperspectral imaging microscopy

Abstract

Sidewall damage is widely recognized as a critical factor limiting the efficiency and reliability of micro-light-emitting diodes (micro-LEDs). However, its spatial impact region and transient manifestation mechanisms remain insufficiently understood. This work employs ultrafast-gated hyperspectral imaging microscopy in conjunction with scanning electron microscopy (SEM) to perform spatial-spectral-temporal-resolved electroluminescence characterization of GaN-based micro-LEDs, achieving precise localization of the sidewall impact region (SIR) with a pixel-sampling resolution of 72 nm. Based on joint analysis of time-resolved spectral parameters, fluorescence lifetime distributions, and SEM morphology, two quantitative metrics, namely, the SIR and the sidewall impact index (SII), are proposed to characterize the spatial extent and the overall strength impacted by the sidewall effect. The results indicate that the influence of sidewall effects extends well beyond the geometric mesa boundary and becomes more pronounced in smaller devices. By combining the SIR and SII metrics, a quantitative framework is established to precisely evaluate sidewall etching-induced perturbations in carrier recombination, providing experimental guidance for sidewall passivation optimization and micro-LED device design.