Photo-ionization spectra for alloy-induced configurations of Si–DX center in AlGaAs

Abstract

We report, for the first time, the spectral dependencies of photo-ionization cross section for individual alloy-induced configurations in Si-doped AlxGa1−xAs (x=0.15). We analyzed the build-up transients of the persistent photoconductivity at 77K, in the spectral range λ=0.88–1.1μm. They were obtained by measuring Hall electron concentration as a function of time in the sample illuminated by the monochromatic light. The measured transients Δn(t) were resolved into three exponential components. We demonstrate that they represent the photoionization of different local configurations of DX center (DX1–DX3). We found that the photo-ionization threshold for different DX configurations varies by the amount practically equal to the variation in their thermal energies. The spectral dependencies found here explain well the previously reported threshold dependence on the initial filling of the DX states.