Observation of a two-dimensional hole gas in boron-doped Si0.5Ge0.5/Ge heterostructures

Abstract
The Hall mobility and magnetoresistance of Si0.5Ge0.5/Ge heterostructures grown by molecular beam epitaxy have been studied in the temperature range 1.5<TT=1.5 K indicate that selective doping of the alloy with boron generates a two‐dimensional hole gas in the Ge. The oscillation period yields a surface carrier density of 2×1012 cm2, in reasonable agreement with the value of 3×1012 cm2 obtained by Hall measurements. The mobility at T=4.2 K in a sample with an undoped alloy setback layer of 4 nm was μH=3.2×103 cm2/V s and in other samples was found to decrease with decreasing setback layer thickness.