It was observed that highly Se-doped material, which was normally opaque to far infra-red radiation, became transparent at hydrostatic pressures above 9.8kbar. This behavior could be explained by the transformation of Se shallow donors into Se-DX centers. Under this assumption, the position of the Se-DX energy level at zero pressure was calculated to lie at 0.08eV above the conduction band under atmospheric pressure. The onset of transparency permitted the observation of several multi-phonon absorbance features. Six of them were attributed to 2-phonon absorptions. No persistent photoconductivity was observed for the Se-DX centers. It was suggested that this might be an indication that the Se shallow donors changed into deep donors which were associated with ionization energy minima.

Shallow to deep transformation of Se donors in GaSb under hydrostatic pressure H.Navarro-Contreras, F.De Anda-Salazar, J.Olvera-Hernández, L.Hsu, M.D.McCluskey, E.E.Haller: Physical Review B, 1999, 59[12], 8003-7