Cathodoluminescence depth-profiling studies of GaN/AlGaN quantum-well structures

In this paper we evaluate the in-depth homogeneity of GaN epilayers and the influence of electric field present in strained GaN/AlGaN heterostructures and quantum wells on the yellow and "edge" emission in GaN and AlGaN. Our depth-profiling cathodoluminescence measurements show an increased accumula tion of defects at the interface. Inhomogeneities in the doping level are r eflected by the enhancement of the yellow emission in the interface region. The piezoelectric effect is found to strongly reduce the emission from the strained AlGaN quantum-well barriers, We also show that Ga droplets, commo nly found oil surfaces of samples grown in Ga-rich conditions, screen the i nternal electric field in a structure and thus result in a local enhancemen t of the edge emission intensity.