Non-steady-state photo-EMF in beta-Ga2O3 crystals at lambda=457 nm

The non-steady-state photoelectromotive force is excited in a monoclinic gallium oxide crystal at wavelength lambda = 457 nm. The crystal grown in an oxygen atmosphere is insulating and highly transparent for a visible light, nevertheless, the formation of dynamic space-charge gratings and observation of the photo-EMF signal is achieved without application of any electric field to the sample. The dependencies of the signal amplitude on the frequency of phase modulation, light intensity, spatial frequency and light polarization are measured. The material demonstrates the anisotropy along the [100] and [010] directions, namely, there is a small difference in the transport parameters and a pronounced polarization dependence of the signal. The crystal's photoconductivity, responsivity and diffusion length of electrons are estimated for the chosen light wavelength and compared with the ones for other wide-bandgap crystals. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement