Photoluminescence and transport in selectively doped p-GaAs/AlGaAs quantum wells: manifestation of the upper Hubbard band

By selective doping (Be) of the well and barrier regions of GaAs/Al0.3Ga0.7As structures we have realized the situation where the upper Hubbard band (A+ centers) has been occupied by holes in the equilibrium. We studied the temperature behavior of the Hall effect, variable range hopping (VRH) conductivity and the photoluminescence (PL) spectra of the corresponding structures. The experimental data demonstrated that the binding energy of the A+ states significantly increases with respect to 3D case and strongly depends on the well width (9 nm, 15 nm). The localization radii of the A+ states estimated from the transport data are of the order of the well widths.