Crystalline dependence of optical and interfacial properties of InGaN/GaN quantum wells on nonpolar a-plane GaN/r-sapphire

We investigated the optical and the crystal qualities of InGaN/GaN quantum wells (QWs) grown on nonpolar a-plane (1 1 2 0) GaN/r-sapphire by introducing the novel 2-step growth method without low temperature GaN or AlN buffer layer. In spite of achievement of macroscopic specular surface structure of a-plane GaN epilayer, the surface defects were developed after growing InGaN/GaN QWs. The surface defect density of InGaN was decreased by enhancing the crystallinity of a-plane GaN template. From high-resolution X-ray ω/2θ scan, the interfacial qualities of InGaN/GaN QWs would deteriorate with increasing surface defect density. In addition, high PL emission intensity and uniformity of InGaN/GaN QWs were obtained by improving the crystal quality of a-plane GaN/r-sapphire due to the abrupt interfacial quality and the reduction of the surface defect in InGaN active regions.