Higher Light-Extraction Efficiency of Nitride-Based Light-Emitting Diodes with Hexagonal Inverted Pyramids Structures

Abstract

Self-assembled hexagonal inverted pyramid (HIP) structures were formed at the mesa-edge region in the InGaN-based light emitting diodes (LEDs). The HIP structures consisted of the top p-type GaN:Mg layers and the bottom InGaN active layers, and they were fabricated through a bandgap-selective photoelectrochemical (PEC) wet-etching process in a potassium hydroxide solution. In the HIP-LED structures, the light output power was 1.6 times higher and the divergent angle was reduced to 146° compared to a standard LED without PEC treatment. The light emission extracted from the InGaN active layer was scattered in a normal direction through the hexagonal inverted pyramid structures located at the wide mesa-edge regions without depositing any transparent metal contact layer.