Light Emission from the Sidewall Region Dominates the Spectral Broadening of InGaN-Based Red Micro-LEDs

Abstract

InGaN-based red microlight-emitting diodes (micro-LEDs) have demonstrated superiority in monolithic integration microdisplays, and red micro-LEDs grown on silicon substrates are cost-efficient and potentially compatible with pixel driving schemes; however, the spectral broadening and inhomogeneous light emission would greatly limit their applications. Herein, to improve the performance of InGaN-based red micro-LEDs, the origin of the spectral broadening and the inner physics of the local light emission from InGaN-based red micro-LEDs grown on silicon substrates were demonstrated via microscopic hyperspectral imaging. The bright circular light emission with a shorter wavelength from the sidewall region of the micro-LEDs is mainly due to the carrier recombination in localized states, which can result in a deviation of the perceived color. The localization can be attributed to the fluctuation in the well thickness, hindering the realization of a uniform red emission. The results further suggest that reasonable strategies to mitigate the spectral broadening effect from the sidewall region of micro-LEDs are significant for achieving efficient InGaN-based red micro-LEDs with a high perceived color quality.