High efficiency of III-nitride and AlGaInP micro-light-emitting diodes using atomic layer deposition

The reduction in efficiency by shrinking device dimensions of micro-light-emitting diodes (μLEDs) has been identified as one of the main drawbacks in the literature. The decrease in efficiency is attributed to surface recombination and sidewall damage due to dry etching, where the efficiency drop is more severe in the AlGaInP material system because of the higher surface recombination velocity and the greater minority carrier diffusion length, compared to the III -nitride system. In this work, the device performance with and without dielectric sidewall passivation using plasma-enhanced chemical vapor deposition (PECVD) or atomic layer deposition (ALD) are first compared, since PECVD is the common method for dielectric sidewall passivation. It is shown that ALD is more effective in terms of suppressing leakage current and enhancing light output power. Moreover, the efficiency of devices with ALD sidewall passivation is partially recovered, indicating that the efficiency drop in μLEDs can be lessened or mitigated by post-etch fabrication techniques. To further improve the efficiency characteristic, the combination of chemical treatments and ALD sidewall passivation are employed to demonstrate size-independent efficiency performance of III-nitride and AlGaInP μLEDs.