Competition between negative and positive photoconductivity in silicon planar-doped GaAs

Abstract

Photo-Hall free electron concentrations were measured on molecular beam epitaxy grown silicon planar-doped GaAs samples, with silicon nominal concentration ranging from 1.4×1012 to 8.8×1013 cm−2, as function of temperature. We found conclusive results showing competition between positive photoconductivity and negative persistent photoconductivity effects. At temperatures below a critical Tc, the negative photoconductivity effect is dominant, while above Tc the positive effect dominates. We also found some evidence that the positive effect is related to spatial charge separation and that the negative effect is related to the DX center.