Extremely high electron mobility in Si/Ge<i>x</i>Si1−<i>x</i> structures grown by molecular beam epitaxy

Abstract

A modulation-doped Si/GexSi1−x structure was fabricated in which a thin Si layer is employed as the conduction channel for the two-dimensional electron gas. The strained heterostructure is fabricated on top of a low threading dislocation density, totally relaxed, GexSi1−x buffer layer with a linearly graded Ge concentration profile. The mobility of the two-dimensional electron gas as determined from Hall measurements was 1600 cm2/V s at 300 K and 96 000 cm2/V s at 4.2 K. Recently, a 4.2 K mobility of 125 000 cm2/V s was observed from a similar sample.