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/cm 2 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/cm 2 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.
Sanyal et al. (Wed,) studied this question.