Ultrasmall, Ultracompact and Ultrahigh Efficient InGaN Micro Light Emitting Diodes (μLEDs) with Narrow Spectral Line Width

Abstract

Augmented reality and visual reality (AR & VR) micro-displays require micro light emitting diodes (µLEDs) with an ultra-small dimension (≤ 5 µm), high external quantum efficiency (EQE) and narrow spectral linewidth. Unfortunately, dry etching which is the most crucial step for the fabrication of µLEDs in current approaches introduces severe damages, which seems to become an insurmountable challenge for achieving ultra-small µLEDs with high EQE. Furthermore, it is well-known that µLEDs which require InGaN layers as an emitting region naturally exhibit significantly broad spectral linewidth, which becomes increasingly severe towards long wavelengths such as green. In this paper, we have reported a combination of our selective overgrowth approach developed very recently and epitaxial lattice-matched distributed Bragg reflectors (DBRs) embedded in order to address all these fundamental issues. As a result, our µLEDs with a diameter of 3.6 µm and an inter-pitch of 2 µm exhibit an ultra-high EQE of 9% at ~500 nm. More importantly, the spectral linewidth of our µLEDs has been significantly reduced down to 25 nm, the narrowest value reported so far for III-nitride green µLEDs.