Consequences of the silicon donor distribution tail in δ-doped, pseudomorphic AlxGa1−xAs/In1−yGa1−yAs modulation-doped heterostructures

We have investigated the properties of modulation-doped, pseudomorphic AlxGa1−xAs/ InyGa1−yAs heterostructures containing embedded, Si δ-doped GaAs wells. From resistivity and Hall effect measurements, and from Shubnikov–de Haas measurements at 1.6 K, we have determined the charge transport parameters before and after optically induced ionization of the DX centers in the structures. We find a DX center diffusion tail associated with the δ-doped donors extending into the undoped AlxGa1−xAs barrier and spacer layers and conclude that for efficient modulation doping of a quantum well, δ-doping and embedding of the donors within a GaAs well can reduce but not entirely eliminate the effects of DX centers on the charge transport parameters.