Minimizing interface defects and enhancing optical brightness of µLEDs through polymeric encapsulants

The need for high resolution microLED arrays, for applications in chip-level optical interconnects and augmented/virtual reality displays, requires the continuing miniaturization of the LED to reduce the pixel size and enable high pixel density. Miniaturization typically degrades brightness because of surface-related non-radiative recombination. Here we demonstrate a combined dry/wet etching process with polymeric encapsulation to construct InGaN-based microLEDs that show negligible degradation due to sidewall effects for devices having diameters as small as 6 µm. The microLEDs exhibit low surface recombination velocities ( <10 cm s^-1) and high wall plug efficiencies of 20.3% at a current density of $2.5\mathrm{A\; c}{m}^{-2}$ . A simple numerical model is developed to explain the dependence of the microLED performance as a function of the microLED geometry. The model determines the critical microLED diameter at which surface recombination becomes comparable to bulk recombination, marking the onset of surface-limited behaviour.