Optical investigation of shallow acceptor states in GaN grown by hydride vapor-phase epitaxy

The evolution of low-temperature photoluminescence (PL) spectra with the thickness of the layer (3-400 mum) is investigated on high-quality GaN grown by hydride vapor-phase epitaxy. With increasing layer thickness, three acceptor bound exciton peaks are found to reduce in intensity, although the impurity concentrations, measured by secondary ion mass spectrometry, do not depend on the sample thickness. The observed acceptor transitions are attributed to intrinsic defects, originating from the substrate/layer interface and decreasing in density with the thickness of the layer. The optical properties, studied by reflectance, temperature and excitation power dependent PL, are compared to those of homoepitaxial GaN films grown by metalorganic chemical vapor deposition. (C) 2001 American Institute of Physics.