Magnetotransport studies of mobility limiting mechanisms in undoped Si/SiGe heterostructures

Abstract

We perform detailed magnetotransport studies on two-dimensional electron gases (2DEGs) formed in undoped Si/SiGe heterostructures in order to identify the electron mobility limiting mechanisms. By analyzing data from 26 different heterostructures, we observe a strong correlation between the background oxygen concentration in the Si quantum well and the maximum mobility. The highest-quality wafer supports a 2DEG with mobility mu = 160 000 cm(2)/Vs at a density n = 2.17x10(11)/cm(2) and exhibits a metal-to-insulator transition at a critical density n(c) = 0.46x10(11)/cm(2). We extract a valley splitting Delta v similar to 150 mu eV at a magnetic field B = 1.8 T. These results provide evidence that undoped Si/SiGe heterostructures are suitable for the fabrication of few-electron quantum dots.