SELF-CONSISTENT SUBBAND STRUCTURE OF MODULATION-DOPED AlxGa1−xAs-GaAs-AlxGa1−xAs DOUBLE QUANTUM WELLS

Abstract

A detailed theoretical study of the electronic subband structure of a two-dimensional semiconductor system is presented for low temperatures. By considering Si modulationdoped Al x Ga 1−x As-GaAs-Al x Ga 1−x As-GaAs-Al x Ga 1−x As double quantum wells (DQWs), a model is developed in which the interested electronic properties, such as confining potential, energy and wavefunction of the electronic subband, electron density, depletion length, etc., can be calculated self-consistently as function of known material properties, sample growth parameters and experimental conditions. We study the influence of the sample parameters and the applied gate voltage on the electronic properties of the DQWs. The main results are: (i) the electronic properties (e.g. electron density, electronic subband energy, depletion length, etc.) of a DQW are very sensitive to the sample growth parameters and to the applied gate voltage; (ii) the energy separation of symmetric and antisymmetric levels in a DQW depends strongly on the widths of the well layer, the separation of the two quantum wells, and on the gate voltage; (iii) the asymmetric modulation-doping has a relatively weak effect on the electronic subband energies of the DQW; and (iv) the electron density and the population of electrons to the electronic subband in the structure can be varied by applying the gate voltage and/or by changing the width of quantum well.