SCATTERING MECHANISMS AFFECTING HOLE TRANSPORT IN REMOTE-DOPED SI SIGE HETEROSTRUCTURES/

Boron modulation-doped Si/SiGe heterojunctions have been grown by mole cular beam epitaxy. The two-dimensional hole gas formed along the hete rojunction, just inside the alloy, has a sheet density in the range 2- 5 X 10(11) CM-2 and a typical mobility at 5 K of 2000 cm2 V-1 s-1. An explanation for the magnitude of the mobility is sought by considering likely scattering mechanisms, namely those due to remote impurities, interface roughness, alloy disorder, and interface impurities. A self- consistent model is used to determine the sheet density in terms of st ructural and energy parameters and dopant concentrations in the hetero structure. It is shown that the presence of negatively charged impurit ies at the heterojunction provides the basis for a consistent interpre tation of the experimental results.