Investigation of InGaN/GaN Quantum Wells Grown on Sapphire and Bulk GaN Substrates

Abstract

Optical and structural properties were investigated in GaN and InGaN multiple-quantum wells (MQWs) grown on sapphire and bulk GaN substrates by metalorganic chemical vapor deposition (MOCVD). Bulk GaN consists of freestanding single crystals grown by sublimation. It was clearly demonstrated that dislocations in undoped GaN, Si-doped GaN and InGaN well act all as nonradiative recombination centers. The InGaN large and small phase separations formed by dislocations were observed only in the heteroepitaxial samples by cathodoluminescence (CL) and photoluminescence (PL) measurements, respectively. These results indicated that the InGaN compositional fluctuation, which produced a large dispersion of the band tail states, is closely associated with a high density of dislocations.