Quantized Hall effects in high-electron-mobility Si/Ge structures

We discuss magnetotransport in high-mobility modulation-doped Si/Ge heterostructures. For a sample with two-dimensional density of 5.2×${10}^{11}$ ${\mathrm{cm}}^{\mathrm{-}2}$ and mobility 95 000 ${\mathrm{cm}}^2$ ${\mathrm{V}}^{\mathrm{-}1}$ ${\mathrm{s}}^{\mathrm{-}1}$ (125 000 ${\mathrm{cm}}^2$ ${\mathrm{V}}^{\mathrm{-}1}$ ${\mathrm{s}}^{\mathrm{-}1}$ after illumination), we observe Hall plateaus at filling factors as high as 24. The valley splitting as well as the spin splitting is resolved. For a lower-density sample, convincing indications of the ν=2/3 fractional quantized Hall state are observed.