Epitaxial growth and optical properties of semipolar (1122) GaN and InGaN/GaN quantum wells on GaN bulk substrates

摘要

GaN and InGaN/GaN multiple quantum well (MQW) were grown on semipolar (1122) GaN bulk substrates by metal organic vapor phase epitaxy. The GaN homoepitaxial layer has an atomically flat surface. Optical reflection measurements reveal polarization anisotropy for the A, B, and C excitons. Free A excitons dominate the photoluminescence (PL) spectrum at 10 K and are accompanied by a weaker, sharp doublet emission due to neutral donor-bound excitons. The InGaN/GaN MQW grown on a GaN homoepitaxial layer involves fast radiative recombination processes. The PL decay monitored at 428 nm can be fitted with a double exponential curve, which has lifetimes of 46 and 142 ps at 10 K. These values are two orders of magnitude shorter than those in conventional c-oriented QWs and are attributed to the weakened internal electric field. The emissions from GaN and MQW polarize along the [1100] direction with polarization degrees of 0.46 and 0.69, respectively, due to the low crystal symmetry.