Regrown Exitaxy for Efficient Red Micro-LEDs (REER-LEDs)

Red micro-LEDs are inefficient compared to their green and blue counterparts which limits the pixel density in RGB micro-LED displays. The size-dependent efficiency droop is related to surface recombination, which is proportionally more important in small micro-LEDs. PSI and UT Austin are addressing the size-dependent efficiency droop by burying junctions inside of the micro-LED structure, thereby avoiding current pathways that traverse the surface. By geometrically avoiding surface currents, we suppress surface recombination as a non-radiative recombination channel, leading to high external quantum efficiency. Our technique is compatible with RGB display integration and produces devices that are inherently self-passivated, contributing to long device lifetime. The combination of advantages offered by the regrowth technique will enable high-efficiency RGB near-eye displays and transmitters for optical communications.