QUANTUM TRANSPORT IN PERIODICALLY DELTA-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 Shubn ikov-de Haas spectrum the quantum mobilities associated with individua l minibands were estimated for each sample. The sheet density of Si at oms in each doping plane was fixed at approximately 2.5 x 10(12) cm(-2 ) in all samples and the doping period was varied in the range 40-1000 Angstrom. The quantum mobilities obtained experimentally are compared with theoretical calculations using the random phase approximation to describe the screened interaction between electrons and charged imo p urities. The theory describes qualitatively the results of the experim ent, i.e. an increase of the quantum mobility with the index of the mi niband, and a decrease in the mobility in all minibands when the dopin g period is made shorter (with a weak maximum at intermediate values o f the doping period). Various possible improvements of the model are s uggested.