THERMALLY ACTIVATED INTERSUBBAND AND HOPPING TRANSPORT IN CENTER-DOPED P-TYPE GAAS ALXGA1-XAS QUANTUM-WELLS/

We present variable temperature resistivity and magnetotransport data for GaAs/AlxGa1-xAs quantum wells, which are Be doped in the central p art of the wells at doping concentrations ranging from moderate levels to well above the degenerate limit. We provide an investigation of po ssible transport mechanisms. For nondegenerate structures, the activat ion of free carriers with a measured activation energy of E(act)=29-36 meV is close to the binding energy of the Be acceptor in Al0.3Ga0.7As /GaAs center-doped quantum wells. The dopant concentration correspondi ng to the transition from being nondegenerate to the degenerate limit is <6x10(18) cm(-3). For degenerate conditions, the variable-range-hop ping 2D transport with rho similar to exp(T-0/T)(1/3), Mott's law, whi ch is observed at lower temperatures, occurs due to the strong localiz ation of holes in the impurity potential fluctuations. For higher temp eratures, the observed thermally activated transport is discussed in t erms of the excitation of holes from the symmetric ground state into t he antisymmetric excited states. The calculated intersubband energies according to a self-consistent solution of the coupled Poisson and Sch rodinger equations are in good quantitative agreement with the experim ental data.