Hall and photo-Hall measurements were performed on GaAs/AlAs short-period superlattices which were selectively doped with Si. The dopant was introduced selectively into the GaAs or AlAs layers, or at the interface. A superlattice which was doped uniformly in both layers was investigated for comparison. It was found that the electrical properties were controlled by DX deep donors which lay in the gap of the superlattice. The Hall data were explained in terms of a model which took account of the existence of two DX deep donors and a shallow donor which were both related to the Si impurity. It was found that the Si donor state in AlAs lay 0.06eV below the Si donor state in GaAs. The ionization energies of the DX states in GaAs and AlAs were calculated in order to account for the experimental results. The interpretation of Hall data in selectively doped samples required the assumption of Si segregation during epitaxy.

P.Sellitto, P.Jeanjean, J.Sicart, J.L.Robert, R.Planel: Journal of Applied Physics, 1993, 74[12], 7166-72