We report the excitation of the non-steady-state photo-electromotive force in a
monoclinic gallium oxide crystal. The crystal grown in an excess of oxygen is insulating and
very transparent for a visible light, but this, however, does not prevent us from the formation
of dynamic space-charge gratings and observation of the photo-EMF signal at λ=532 nm.
The induced ac current is studied for the cases of zero external electric fields. The
dependencies of the signal amplitude versus the frequency of phase modulation, light
intensity, spatial frequency are measured. The photoconductivity and diffusion length of
electrons are estimated for the chosen light wavelength.
Keywords: wide-bandgap semiconductors; non-steady-state photo-electromotive force.
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