Extrinsic photoconductivity in high-resistivity GaAs doped with oxygen

Abstract
We report photoconductivity measurements on melt‐grown high‐resistivity GaAs : O, taken at 80, 190, 275, and 295 K. The data are shown consistent with a model involving an impurity‐to‐conduction band transition. The impurity binding energy is found at 0.69 eV from the conduction band, at 0 K. This energy decreases with increasing temperature. The data also indicate a Franck‐Condon shift of 0.14 eV and a center of axial or lower symmetry. These results enable us to link our observations to earlier reports on GaAs : O and to conclude that they all refer to the ’’0.75‐eV’’ center associated with the presence of oxygen.