Study of MBE-Grown GaN/AlGaN Quantum Well Structures by Two Wavelength Excited Photoluminescence

Abstract

We report experimental results of two wavelength excited photoluminescence (TWEPL) applied to GaN/Al0.2Ga0.8N multiple quantum well structures grown by plasma assisted molecular beam epitaxy. An increase or a decrease in photoluminescence (PL) indicate the presence of trap centers with dissimilar characteristics for each case. In these samples, a spatial inhomogeneity of trap distribution originating from the growth process was detected due to different change in PL for distinct regions. Also a time-dependent phenomenon in PL was observed: after a continuous mid-term irradiation with UV light (4.12 eV), the amount of change in PL, which is characteristic of TWEPL, became nil. We argue this phenomenon is a complex issue that can be due to migration of native defects or a kind of saturation process involving trap centers.