Fabrication and improved properties of InGaN-based LED with multilayer GaN/nanocavity structure

Abstract

Herein we first use the multilayer nanoporous GaN (MNP-GaN) as a substrate for the regrowth of light emitting diode (LED) with InGaN/GaN multiple quantum wells. The large-scale MNP-GaN structure, prepared by a simplified electrochemical etching method in an oxalic acid solution, shows the striking difference in porosity between n-GaN and n+-GaN layer, which is due to the significant difference in the carrier concentration. After the regrowth process, the nanopores in the MNP-GaN layer can be transformed into nanocavities ascribed to mass-transport from high-curvature to low-curvature areas. The photoluminescence lifetime and luminescence intensity of the LED with multilayer GaN/nanocavity structure show a sixfold enhancement compared to those of the reference sample. The luminescence enhancement can be ascribed to the high crystalline quality of multiple quantum wells due to the stress relaxation and the low density of dislocations, as well as the light reflection and scattering effect of the bottom multilayer GaN/nanocavity structures.