Quantum transport in periodically δ-doped GaAs

The Shubnikov-de Haas spectra of GaAs samples with a periodical doping with Si were measured at 4.2 K using fields of 0–14 T. From the Shubnikov-de Haas spectrum the quantum mobilities associated with individual minibands were estimated for each sample. The sheet density of Si atoms in each doping plane was fixed at approximately 2.5 × 10¹² cm^?2 in all samples and the doping period was varied in the range 40–1000 Å. The quantum mobilities obtained experimentally are compared with theoretical calculations using the random phase approximation to describe the screened interaction between electrons and charged impurities. The theory describes qualitatively the results of the experiment, i.e. an increase of the quantum mobility with the index of the miniband, and a decrease in the mobility in all minibands when the doping period is made shorter (with a weak maximum at intermediate values of the doping period). Various possible improvements of the model are suggested.