Large magnetoresistance of a dilutep-Si/SiGe/Siquantum well in a parallel magnetic field

Abstract

We report the results of an experimental study of the magnetoresistance ${\ensuremath{\rho}}_{xx}$ in two samples of $p\text{-Si}/\text{SiGe}/\text{Si}$ with low carrier concentrations $p=8.2\ifmmode\times\else\texttimes\fi{}{10}^{10}\text{ }{\text{cm}}^{\ensuremath{-}2}$ and $p=2\ifmmode\times\else\texttimes\fi{}{10}^{11}\text{ }{\text{cm}}^{\ensuremath{-}2}$. The research was performed in the temperature range of 0.3--2 K in the magnetic fields of up to 18 T, parallel to the two-dimensional (2D) channel plane at two orientations of the in-plane magnetic field ${B}_{\ensuremath{\parallel}}$ against the current $I$: ${B}_{\ensuremath{\parallel}}\ensuremath{\perp}I$ and ${B}_{\ensuremath{\parallel}}\ensuremath{\parallel}I$. In the sample with the lowest density in the magnetic field range of 0--7.2 T, the temperature dependence of ${\ensuremath{\rho}}_{xx}$ demonstrates the metallic characteristics $(d{\ensuremath{\rho}}_{xx}/dT>0)$. However, at ${B}_{\ensuremath{\parallel}}=7.2\text{ }\text{T}$ the derivative $d{\ensuremath{\rho}}_{xx}/dT$ reverses the sign. Moreover, the resistance depends on the current orientation with respect to the in-plane magnetic field. At ${B}_{\ensuremath{\parallel}}\ensuremath{\cong}13\text{ }\text{T}$ there is a transition from the dependence $\text{ln}(\ensuremath{\Delta}{\ensuremath{\rho}}_{xx}/{\ensuremath{\rho}}_{0})\ensuremath{\propto}{B}_{\ensuremath{\parallel}}^{2}$ to the dependence $\text{ln}(\ensuremath{\Delta}{\ensuremath{\rho}}_{xx}/{\ensuremath{\rho}}_{0})\ensuremath{\propto}{B}_{\ensuremath{\parallel}}$. The observed effects can be explained by the influence of the in-plane magnetic field on the orbital motion of the charge carriers in the quasi-2D system.