Demonstration of 2.71% External Quantum Efficiency at 630 nm in Singular 2 μm Red InGaN Micro-LEDs on Porous GaN for AR/VR Applications

Abstract

Next-generation augmented/virtual reality (AR/VR) headsets require ultrasmall (<5 μm) micro-LEDs. The III-Nitride material system is used for highly efficient blue and green devices. Due to the low efficiency of red InGaN LEDs, AlInGaP is used for red emission. However, AlInGaP-based red micro-LEDs suffer from intense size-dependent efficiency reduction. Using topology-free porous pseudo-substrates, we fabricated ultra-small red InGaN micro-LEDs with a lateral dimension of 2 μm, achieving a peak external quantum efficiency (EQE) of 2.71% at 630 nm under 2.5 A/cm² in an integrating sphere. To the best of our knowledge, this is the highest reported peak EQE for singular (nonarrayed) InGaN micro-LEDs with a lateral dimension less than 5 μm and a peak wavelength greater than 620 nm. Based on finite-difference time-domain simulations, with silicone encapsulation (n = 1.54), the EQE could potentially increase to 4.4%. The peak EQE occurs at a low current density of 2.5 A/cm² and, along with the small device size (2 μm), makes it attractive for AR/VR applications, which require low power consumption and high pixel density.