The effect of cooling conditions upon transport in Si-doped AlxGa1–xAs was studied. It was shown that rapid cooling induced a freezing-out of electrons; similar to that observed after photo-ionization at low temperatures. By quenching samples into liquid N, a multi-component structure was revealed, with 3 resolved peaks on transport curves at a relatively low Al composition (x = 0.28). These peaks were attributed to the non-resonant 3Al-, 2Al- and 1Al–DX levels.

Evidence of Three DX Centers in Al0.28Ga0.72As:Si from Hall Experiments. A.Triki, F.Rziga-Ouaja, H.Mejri, A.Selmi: Journal of Applied Physics, 2003, 93[12], 9769-72