Photo-induced transition in the conduction regime of a two-dimensional system

We report on experimental evidence of a transition in the conduction regime of a two-dimensional electron gas in GaAs with a single layer of silicon p lanar doping. The magnetic field and temperature dependence of the electric al conductivity show a gradual change from activated to metallic type condu ction under illumination with below bandgap radiation. We propose that the mechanism for the change in the conduction regime occurs via an EL2-like de fect. The electrons photo-excited to the conduction band from this deep lev el are spatially separated from their parent defects due to the high intrin sic electric field. At low temperatures the return tunneling probability of these electrons is low and the concentration of carriers in the potential well in the region of the doping layer is adjusted by the total light dose that the sample has been submitted to.