Transport and Photoelectrical Properties of Gallium Arsenide Containing Deep Acceptors

Abstract

An analysis of Hall-effect and optical measurements shows that Ni, Co, and Mn form relatively deep and compact acceptors in GaAs, with activation energies of 0.20, 0.16, and 0.09 eV, respectively. Conduction by free valence-band holes is augmented at low temperatures by impurity conduction in crystals with heavy doping and strong compensation. The photoabsorption cross section for manganese (which we find to be smaller than hitherto reported) and for cobalt can be viewed as the sum of a Lucovsky-like δ-function potential model for photoionization, and smaller but recognizable contributions due to transitions of holes into the V3 ``split-off'' band, 0.35 eV below the upper valence bands. We have observed the spectral dependence of photoconductivity in these three doped GaAs systems from the intrinsic peak down to the extrinsic threshold.