X-ray induced persistent photoconductivity in Si-doped Al_0.35Ga_0.65As

We demonstrate that x-ray irradiation can be used to induce an insulator-metal transition in Si-doped Al_0.35Ga_0.65As, a semiconductor with DX centers. The excitation mechanism of the DX centers into their shallow donor state was revealed by studying the photoconductance along with fluorescence. The photoconductance as a function of incident x-ray energy exhibits an edge both at the Ga and As K edge, implying that core-hole excitation of Ga and As are efficient primary steps for the excitation of DX centers. A high quantum yield (≫1) suggests that the excitation is indirect and nonlocal, due to secondary electrons, holes, and fluorescence photons.