Undoped epitaxial films of α-Ga 2 O 3 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 α-Ga 2 O 3 films. All grown α-Ga 2 O 3 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 α-Ga 2 O 3 samples are close to the position of dominant electron and hole traps in well documented β-Ga 2 O 3 crystals and films.
ASJC Scopus subject areas
- Materials Science(all)