Fabrication of Ge channels with extremely high compressive strain and their magnetotransport properties

Abstract

Ge channels with extremely high compressive strain were fabricated. SiGe buffer layers with Ge concentration from 40% to 65% were grown on Si substrates by gas source molecular beam epitaxy (MBE), and subsequently modulation-doped Ge channel structures were grown on the buffers by solid source MBE. High crystal quality Ge channel layers with the compressive strain as high as 2.4% were realized due to low-temperature growth. Magnetotransport properties were investigated for the structures. Well-resolved Shubnikov–de Haas oscillations were observed and Dingle ratios beyond 10 were obtained. This indicated that remote impurity scattering is dominant rather than interface roughness scattering, reflecting high-quality channel layers in spite of the large strain. Moreover, reduced effective masses due to the large strain were demonstrated.