Low-density spin-polarized transport in two-dimensional semiconductor structures: Temperature-dependent magnetoresistance of Si MOSFETs in an in-plane applied magnetic field

The temperature dependence of two-dimensional (2D) magnetoresistance in an applied in-plane magnetic field is theoretically considered for electrons in Si MOSFETs within the screening theory for long-range charged impurity scattering limited carrier transport. In agreement with recent experimental observations we find an essentially temperature-independent magnetoresistivity for carrier densities well into the 2D metallic regime due to the field-induced lifting of spin and, perhaps, valley degeneracies. In particular the metallic temperature dependence of the ballistic magnetoresistance is strongly suppressed around the zero-temperature critical magnetic field (B-s) for full spin polarization, with the metallic temperature dependence strongest at B=0, weakest around B similar to B-s, and intermediate at B > B-s.