Improvement in Crystalline Quality of InGaN-Based Epilayer on Sapphire via Nanoscaled Epitaxial Lateral Overgrowth

Abstract

In this study, a high-performance GaN-based light-emitting diode (LED) was achieved using a nanocolumn patterned sapphire substrate (NCPSS) with low-pressure metal-organic chemical vapor deposition (LP-MOCVD). The surface roughness was evaluated by atomic force microscopy (AFM). The mechanisms of carrier localization in the GaN-based LED fabricated on NCPSS were discussed referring to the results obtained from the power-dependent photoluminescence measurements. Moreover, from the transmission electron microscopy (TEM) image, the threading dislocation densities (TDDs) through the GaN-based LED fabricated on NCPSS were found to be about 10 times lower than those fabricated on planar substrates. Finally, the internal quantum efficiency (IQE) of the GaN-based LED fabricated on NCPSS was as high as 48% at 30 mW, corresponding to a current of 20 mA, which is higher than that of a GaN-based LED fabricated on a planar sapphire substrate by 8%. The use of NCPSS is suggested to be effective for elevating the emission efficiency of the GaN-based LED owing to an improvement in crystal quality. (C) 2010 The Japan Society of Applied Physics