Donor binding energy and thermally activated persistent photoconductivity in high mobility (001) AlAs quantum wells

A doping series of AlAs (001) quantum wells with Si δ -modulation doping on both sides reveals different dark and postillumination saturation densities, as well as temperature dependent photoconductivity. The lower dark two-dimensional electron density saturation is explained assuming deep binding energy of ΔDK =65.2 meV for Si donors in the dark. Persistent photoconductivity (PPC) is observed upon illumination, with higher saturation density indicating shallow postillumination donor binding energy. The photoconductivity is thermally activated, with 4 K illumination requiring postillumination annealing to T=30 K to saturate the PPC. Dark and postillumination doping efficiencies are reported.