Binding energy of an oxygen-related defect in modulation-doped quantum wires

This work is devoted to a theoretical study of the microscopic mechanism that gives rise to the lateral confinement of modulation-doped quantum wires. We have given special attention to an accurate description of the fabrication process and the actual geometry of the samples. The mechanism proposed consists of the formation of a defect presumably related to oxygen atoms (OX) which is able to capture electrons from the quantum well. We obtain significant agreement not only qualitatively but also quantitatively with all the available experimental information, which includes optical properties and phenomenological aspects of the fabrication process. To obtain this agreement it was necessary to establish the spatial distribution of the OX and their binding energy: they should be placed close to the ${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As/GaAs interface while their binding energy (measured with respect to the bottom of the conduction band of the ${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As) should be (${\mathrm{V}}_0$±5) meV (${\mathrm{V}}_0$ being the conduction-band offset). The model also describes interesting phenomena, among them how to improve the quality of the lateral confinement.