Optical and electrical properties of GaN micron-scale light-emitting diode Original Research Article

The III-nitride-based micron-scale light-emitting device (LED) could suppress the current crowding effect and increase the light extraction from micro-cavity. The uniform and high light extraction efficiency could be achieved with micro-LEDs. No reliable micro-LEDs or micro-LEDs array could be fabricated due to the etching damage and p-type ohmic contact stability. The single micro-LEDs with mesa-structure were fabricated with device size changed from 15 to 5 μm. The 3 μm single micro-LEDs with ring-structure were fabricated by lithography technology in diffraction mode. In low current injection (0–2 V), the tunneling-recombination current through the shallow state was increasing while the device size was shrinking. In middle current injection (2–2.6 V), the tunneling recombination through the deep gap state was also increasing due to the etching damage. Under high-current injection (>2.6 V), the current transport was described by drift–diffusion-recombination model and Schottky-like p-type contact. The high fluctuation of the series resistance and high ideality factor was observed in micro-LEDs. The post-treatment with hot KOH solution was used to reduce the etching damage. After post-treatment, the etching damage was reduced with mesa-structure. The micro-ring device was destroyed after post-treatment. No power saturation with 15×15 um2 micro-LEDs were observed under high-current density injection with electroluminescence measurement.