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

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 μ=160000 cm2/Vs at a density n=2.17×1011/cm2 and exhibits a metal-to-insulator transition at a critical density nc=0.46×1011/cm2. We extract a valley splitting Δv∼150μeV 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.