Epitaxial growth and optical properties of semipolar (112¯2) GaN and InGaN∕GaN quantum wells on GaN bulk substrates

GaN and InGaN∕GaN multiple quantum well (MQW) were grown on semipolar (112¯2) 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 10K 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 428nm can be fitted with a double exponential curve, which has lifetimes of 46 and 142ps at 10K. 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 [11¯00] direction with polarization degrees of 0.46 and 0.69, respectively, due to the low crystal symmetry.