Optical Characterization of Double Peak Behavior in {10(1)over-bar1} Semipolar Light-Emitting Diodes on Miscut m-Plane Sapphire Substrates

Abstract

(10 (1) over bar1) semipolar GaN-based light-emitting diodes (LEDs) grown on 1 degrees miscut m-plane sapphires substrates via metal organic chemical vapor deposition showed undulated surface morphology with ridges and valleys. On the ridge regions, two dominant emission peaks, one at a shorter wavelength (similar to 438 nm) and one at a longer wavelength (similar to 490 nm), were observed using electroluminescence and micro-photoluminescence. In the valley regions, the longer peak was observed to be significantly quenched due to the grain boundary. The origin of the longer peak is believed to be not only inhomogeneous distribution of In composition in multiple quantum wells (MQWs) but also strong localization around the ridge region. Moreover, thickness variation of faceted MQWs could be associated with the peak broadening in {10 (1) over bar1} semipolar LEDs. The results were also confirmed by cathodoluminescence and cross-sectional transmission electron microscopy. (C) 2012 The Japan Society of Applied Physics