Output power enhancements of nitride-based light-emitting diodes with inverted pyramid sidewalls structure

This study presents nitride-based light-emitting diodes (LEDs) with inverted pyramid sidewalls by chemical wet etching nitride epitaxial layers and investigates the chemical wet etching mechanism of inverted pyramid sidewalls. It is well known that chemical etching solutions such as KOH, H2SO4 and H3PO4, to selectively etch the N-face GaN but not the Ga-face GaN. In this study, the N-face GaN was exposed around the chip by laser scribing at the GaN/sapphire interface. These channels provided paths for the chemical etchant to flow and allow the etching solution to further contact with and etch the exposed bottom N-face GaN. Chemical etching of the chip sidewalls formed the inverted hexagonal pyramid shape with {10 −1 −1} facets. Findings show that inverted pyramid sidewalls enhance 20 mA LED output power by 27% for LEDs, with chemical etching of the chip sidewalls for 4 min, compared to the conventional LED. The larger LED output power is attributed to increased light extraction efficiency by inverted pyramid sidewalls.