Formation and Markedly Enhanced Optical Properties of Large-Area Nanoporous InGaN-Based LEDs with Nanoporous GaN Distributed Bragg Mirrors

Abstract

Compared with nitric acid solution, oxalic acid solution has the advantages of safety, environmental protection, and a controllable etching rate. Largearea (20.3 cm 2 ) nanoporous InGaN-based LEDs with nanoporous GaN distributed Bragg mirrors (NP LEDs) are prepared by a combination of doping, wet etching in oxalic acid solution, and metal−organic chemical vapor deposition (MOCVD). Compared with the epitaxial growth of LEDs (EG LEDs), NP LEDs show a decreased surface roughness, an enhanced luminescence intensity, and a blue shift of the luminescence peak. The enhancement of luminescence intensity can be attributed to the enhancement of internal quantum efficiency related to the increased crystal quality of MQWs, as well as increasing light extraction efficiency caused by the light-guiding effect of nanopore arrays in MQWs and the light reflection effect of nanoporous GaN distributed Bragg mirrors. The blue shift phenomenon is due to the stress relaxation of MQWs and the decreased In content.