The electrical properties of various short-period superlattices which were uniformly doped with Si were investigated. Hydrostatic pressure was used to capture electrons from the conduction miniband in deep donor states that were associated with the large lattice relaxation of the Si donor in GaAs, in AlAs and at the GaAs/AlAs interface. The ionization energies and densities of various deep donors were determined. It was found that a 2-band model of conduction, which assumed the existence of 3 donor states (discrete structure of the Si-DX center), accounted for the Hall data for all of the samples. The application of hydrostatic pressure permitted the variation of the miniband energy in some samples, and led to an improved determination of the donor energies and concentrations. When the AlAs growth rate was equal to half of the GaAs growth rate, the fraction of DX states decreased in AlAs, whereas the fraction of DX states increased at the interface; thus indicating marked Ga/Al cation exchange across the interface.

Investigation of DX center in silicon-doped GaAs-AlAs short-period superlattices F.Bosc, J.Sicart, J.L.Robert: Journal of Applied Physics, 1999, 85[9], 6520-5