Enhancement in light output of InGaN-based microhole array light-emitting diodes

InGaN-based microhole array light-emitting diodes (LEDs) with hole diameters (d) of 3-15 μm were fabricated using self-aligned etching. The effects of size on the device characteristics, including current density-voltage and light output-current density, were measured and compared with those of conventional broad-area (BA) LEDs fabricated from the same wafer. The electrical characteristics of the devices are similar to those of conventional BA LEDs. The light output from the microhole array LEDs increases with d up to 7 μm. However, the light output declined as d increased further, perhaps because of the combination of the enhancement in extraction efficiency caused by the large surface areas provided by the sidewalls and the decrease in area of light generation by holes in the microhole array LEDs. The ray tracing method was used with a two-dimensional model in TracePro software. The findings indicate that an optimal design can improve the light output efficiently of the microhole array LEDs.