Magnetotransport of epitaxial Si/Ge layers on Si

Magnetotransport measurements at magnetic fields up to 14 T were performed on Si/Ge layers grown on n-type (001) Si by MBE. The envelope for possible mobility distributions was evaluated from the magnetic field dependence of the components of the conductivity tenser. An ambipolar current was revealed from these data for boron-doped homoepitaxial layers such as for (Si/Ge) superlattices. For the undoped samples the free carrier concentrations measured are discussed taking into account the band discontinuities in the heterostructure and defects due to dislocations. For example, an energy distance of about 0.1 eV between the conduction band minimum and the valance band maximum in the strained Si and Ge layers, respectively, was deduced for a long period superlattice from the free carrier concentration of 2 x 10(18) cm(-3).