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=65.2meV 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 4K illumination requiring postillumination annealing to T=30K to saturate the PPC. Dark and postillumination doping efficiencies are reported.