γ-ray enhanced quenching phenomenon of photoconductance in undoped and In-doped semi-insulating GaAs

Abstract
In undoped and In-doped semi-insulating GaAs with various dislocation densities, we have found that the quenching phenomenon of photoconductance is enhanced by γ irradiation above 107 rad at room temperature. In particular, this effect is obvious for crystals with dislocation densities of 10–103/cm2. The new stage induced by γ irradiation is found around 100 K and disappears gradually by annealing above 300 °C. The time dependence of photoconductance suggests the existence of the newly introduced state assisting the transition from a normal midgap electron trap (EL20) to a metastable state (EL2*) in the semi-insulating materials.