High mobility SiGe heterostructures fabricated by low-energy plasma-enhanced chemical vapor deposition

We present results obtained on modulation-doped quantum wells with compressively strained Ge channels. The heterostructures have been grown by low-energy plasma-enhanced chemical vapor deposition (LEPECVD). Magnetotransport measurements were carried out both on van der Pauw squares and lithographically defined Hall bars. The 2 K hole mobility increases with sheet density, and exceeds 105 cm2 V−1 s−1 below 40 K for carrier densities above 8 × 1011 cm−2. It is dominated by remote impurity scattering, according to linear transport theory calculations. The same conclusion follows from the Dingle ratios of 5–10 derived from the low-field longitudinal magnetoresistance. Room-temperature channel mobilities were extracted from the magnetic field dependence of longitudinal and transverse magnetoresistance by means of mobility spectrum analysis. We obtained 2940 cm2 V−1 s−1 at a sheet hole density of 5.7 × 1011 cm−2