Electrical properties, structural properties, and deep trap spectra of thin α-Ga2O3 films grown by halide vapor phase epitaxy on basal plane sapphire substrates

Undoped epitaxial films of alpha-Ga2O3 were grown on basal plane sapphire substrates by halide vapor phase epitaxy (HVPE) in three different modes: standard HVPE, HVPE with constant flow of Ga and pulsed supply of O-2 (O-2-control growth regime), and with constant flow of O-2 and pulsed delivery of Ga (Ga-control growth fashion). The best crystalline quality as judged by x-ray symmetric and asymmetric reflection half-widths and by atomic force microscopy morphology profiling was obtained with the O-2-control deposition, and these results appear to be the best so far reported for alpha-Ga(2)O(3)films. All grown alpha-Ga2O3 epilayers were high-resistivity n-type, with the Fermi level pinned near E-c - 1 eV deep traps. Photoinduced current transient spectra also showed the existence in standard HVPE samples and samples grown under the O-2-control pulsed growth conditions of deep hole traps with levels near E-v + 1.4 eV whose density was suppressed in the Ga-control pulsed HVPE samples. The levels of the dominant deep traps in these alpha-Ga2O3 samples are close to the position of dominant electron and hole traps in well documented alpha-Ga2O3 crystals and films. (C) 2018 Author(s).