Quantitative analysis of substrate effects on thermal characteristics in InGaN/GaN-based micro-LEDs

Abstract Indium gallium nitride/gallium nitride (InGaN/GaN)-based micro light-emitting diodes (microLEDs) have emerged as promising candidates for high-resolution display, sensor, and optogenetic applications. However, the reduction in device size increases the influence of self-heating caused by sidewall recombination, degrading junction temperature ( T j ) and optical stability. In this study, we systematically investigated the thermal dissipation behavior of InGaN-based lateral and flip-chip (FC) microLEDs through calibrated finite-element simulations in COMSOL Multiphysics. Thermal resistance ( R TH ) and T j were analyzed with respect to substrate material, Silicon (Si) and sapphire, and thickness. For lateral devices under a power density of 400 W cm −2 , thinning the Si substrate from 1150 to 30 μ m reduced R TH by 96% and T j by 37 K. Si-based devices exhibited up to 70% lower R TH compared to sapphire. These reductions also suppressed emission peak shifts and full-width-half-maximum broadening by up to 98.7%. In FC configurations, substrate thinning had minimal effect, with thermal performance governed by bump height and thermal conductivity. This study provides the first comprehensive simulation-based framework for quantifying substrate-dependent thermal effects in microLEDs, offering important design guidelines to improve reliability and optical performance in microLED applications.