Origins of Inhomogeneous Light Emission From GaN-Based Flip-Chip Green Micro-LEDs

Abstract

Spatially resolved electroluminescence emitted through the sapphire substrate of GaN-based flip-chip green microscale light-emitting diodes with $20\times 20\,\,\mu \text{m}^{\text {2}}$ mesas has been collected via microscopic hyperspectral imaging. The current crowding is identified in the central region of the mesa, corresponding to the position of the p-pad. The bright-spot emissions at the edges of the mesa originate from localized potential energy valleys. This letter suggests that the comprehensive information about current crowding and the distribution of the light emission across the mesa of microscale light-emitting diode can be obtained by capturing spatially resolved light emission from the side of the transparent substrate.