DEEP TRAPS SPECTRA IN UNDOPED GAN FILMS GROWN BY HYDRIDE VAPOR PHASE EPITAXY UNDER VARIOUS CONDITIONS

Decreasing the residual donors density and deep tra ps spectra densities in undoped GaN films grown by Hydride Vapor Phase Epitaxy (HVPE) is very important for promoting the use of such material in highvoltage/high-power rectifiers, radiation detectors. In this study we studied the effects of changing t he growth temperature of undoped HVPE GaN films on these properties. The two groups of undoped GaN HVPE samples analyzed in this study were grown at growth temperature being either 850oC or 950oC. Measurements by means of Capacitance-Voltage (C-V) profiling, deep levels transient spectroscopy, Micr o Cathode Luminescence (MCL) spectroscopy and imaging and by Electron Beam Induced Current (EBIC) showed a much lower density of residual donors (by almost two orders of magnitude), of deep electron t raps and hole traps (by about an order of magnitude) and considerably (about 1.5 times) longer diffusion le ngth of charge carriers in the films grown at 850oC comp ared to samples prepared at 950oC. The data obtaine d indicate that there is an optimal reduced growth te mperature (close to 850oC) resulting in lower concentration of shallow donors and deep traps whil e still preserving the high crystalline quality of the layer. This is of paramount importance for device a pplications of HVPE grown undoped GaN films.