Two-dimensional metal-insulator transition and in-plane magnetoresistance in a high-mobility strained Si quantum well -: art. no. 081313

The apparent metal-insulator transition is observed in a high-quality two-dimensional electron system (2DES) in the strained Si quantum well of a Si/Si1-xGex heterostructure with mobility mu=1.9x10(5) cm(2)/V s at density n=1.45x10(11) cm(-2). The critical density, at which the thermal coefficient of low T resistivity changes sign, is similar to 0.32x10(11) cm(-2), a very low value obtained in Si-based 2D systems. The in-plane magnetoresistivity rho(B-ip) was measured in the density range, 0.35x10(11)< n < 1.45x10(11) cm(-2), where the 2DES shows the metalliclike behavior. It first increases and then saturates to a finite value rho(B-c) for B-ip> B-c, with B-c the full spin-polarization field. Surprisingly, rho(B-c)/rho(0)similar to 1.8 for all the densities, even down to n=0.35x10(11) cm(-2), only 10% higher than n(c). This is different from that in clean Si metal-oxide-semiconductor field-effect transistors, where the enhancement is strongly density dependent and rho(B-c)/rho(0) appears to diverge as n -> n(c). Finally, we show that in the fully spin-polarized regime, dependent on the 2DES density, the temperature dependence of rho(B-ip) can be either metalliclike or insulating.