Peculiarities of Silicon-Donor Ionization and Electron Scattering in Pseudomorphous AlGaAs/InGaAs/GaAs Quantum Wells with Heavy Unilateral Delta-Doping
The influence of the concentration of silicon donors on the electron-transport properties of pseudomorphous Al0.25Ga0.75As/In0.2Ga0.8As/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.
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