Peculiarities of Silicon-Donor Ionization and Electron Scattering in Pseudomorphous AlGaAs/InGaAs/GaAs Quantum Wells with Heavy Unilateral Delta-Doping

Abstract

The influence of the concentration of silicon donors on the electron-transport properties of pseudomorphous Al_0.25Ga_0.75As/In_0.2Ga_0.8As/GaAs quantum wells (QWs) in heterostructures with heavy unilateral δ-doping by Si atoms was studied in a broad temperature interval (2.1–300 K). High electron mobility (up to 35700 cm²/(V s)) at T = 4.2 K was observed at a 2D (sheet) electron density of 2 × 10¹² cm^–2 in the QW. A band mechanism limiting the ionization of donors at an increased level of doping is described. The nonmonotonic variation of electron mobility with increasing silicon concentration is explained. A growth in the mobility is related to increase in the Fermi momentum and screening, while the subsequent decay is caused by tunneling-induced degradation of the spacer layer with decreasing potential of the conduction band in the region of δ-Si layer. It is shown that the effect is not related to filling of the upper subband of dimensional quantization.