Extremely high electron mobility in Si/SiGe modulation-doped heterostructures

We report record high electron mobility in modulation-doped Si/SiGe. Samples grown by ultrahigh vacuum chemical vapor deposition (UHV-CVD) with mobility values in the range of 3.2–5.2×105 cm2/V s have been measured at 0.4 K. The current and temperature dependence of the magnetoresistance in those samples have been examined and the scattering times are deduced from these measurements. At high magnetic field (≳10 T), fractional quantum Hall filling factors have been observed, and the corresponding activation energies have been calculated. These are significantly larger than previously reported values in Si/SiGe, and are comparable to those in GaAs/AlGaAs modulation-doped heterostructures with mobility higher than 1×106 cm2/V s.