Nanoepitaxy to improve the efficiency of InGaN light-emitting diodes

Abstract

In Ga N ∕ Ga N blue light-emitting diode (LED) structures are grown on nanoepitaxial lateral overgrown (NELO) GaN template on sapphire substrates by metal organic chemical vapor deposition. Nanopore arrays in SiO2 film are fabricated on the underlying GaN using anodic alumina as etch masks, resulting in a nanoporous SiO2 mask layer with an average nanopore diameter and interpore distance of 60 and 110nm, respectively. The LED on NELO GaN demonstrates low defect density, which is revealed by cross-sectional transmission electron microscopy. More importantly, the LED on NELO GaN demonstrates a higher output power, one order of magnitude higher at 80mA, and an enhancement of the emission efficiency compared to that of the LED on planar GaN. This is mainly attributed to the improvement of light extraction efficiency by random scattering at the interface of the nanoporous SiO2 mask. The nanoporous SiO2 mask acts as both a threading dislocation reduction layer and a light scattering layer to enhance both internal quantum efficiency and external light extraction efficiency. The use of NELO method improves both internal quantum efficiency and external quantum efficiency for III-nitrides based optoelectronic devices.