Hydrogen centers as a probe of V-Ga(2) defects in beta-Ga2O3

While a number of O-H and O-D vibrational lines have been observed for hydrogen and deuterium in beta-Ga2O3, it has been commonly reported that there is no absorption with a component of the polarization E parallel to the [010], or b, axis. This experimental result has led to O-H defect structures that involve shifted configurations of a vacancy at the tetrahedrally coordinated Ga(1) site [V-Ga(1)] and have ruled out structures that involve a vacancy at the octahedrally coordinated Ga(2) site [V-Ga(2)], because these structures are predicted to show absorption for E//[010]. In this Letter, weak O-D lines at 2475 and 2493 cm(-1) with a component of their polarization with E//[010] are reported for beta-Ga2O3 that had been annealed in a D-2 ambient. O-D defect structures involving an unshifted V-Ga(2) are proposed for these centers. An estimate is made that the concentration of V-Ga(2) in a Czochralski-grown sample is 2-3 orders of magnitude lower than that of V-Ga(1) from the intensities of the IR absorption lines.