Low Efficiency Attenuation and Stable Monochromaticity for Non-Polar m-Plane Micro-Ligh-Emitting-Diodes (Micro-LEDs)

In this paper, the gallium nitride (GaN) free-standing non-polar m-plane micro-LEDs and polar c-plane micro-LEDs on patterned sapphire substrate with a 550-nm emission light were fabricated and characterized. Compared with c-plane micro- LEDs suffering from strong quantum confined stark effect (QCSE), the absence of polarization effect in m-plane devices contributed to a lower efficiency attenuation and narrower peak and color shift with elevating current density. Specifically, the peak wavelength shift for c-plane and m-plane micro-LEDs was 81 nm and 8.12 nm respectively from 1 to 500 A/cm², and the efficiency droop ratio was 50.2% for c-plane and 27.2% for m- plane devices from 0.1 to 300 A/cm². Importantly, our m-plane micro-LEDs achieved a stable monochromaticity and wider color gamut under different injection current density (97.9% and 98.2% of Rec. 2020 at 1 and 500 A/cm2).