Decay kinetics of persistent photoconductivity in semiconductors

Kinetic studies of the decay of persistent photoconductivity can decide between competing interpretations. This paper is concerned with the temporal decay of excess conductivity after illumination for low temperatures and spatial carrier separation. The initial decay is rapid since closely spaced carriers recombine; later decay is retarded. Analytic expressions are derived for various trap profiles. Epitaxial GaAs and interfaces of ${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As-GaAs heterostructures are investigated; the results agree with theory, which predicts a decay essentially logarithmic in time.