Research on Semiconductors at Cryogenic Temperatures

摘要

The Hall mobility and magnetoresistance of selectivity doped heterostructures of SixGe1-x/Ge prepared by molecular beam epitaxy (MBE) have been studied in the temperature range 1.5 < T < 300K. Either Al or B was used to dope the alloy p-type. Evidence was found in the B-doped samples with x = 0.5 that a 2DHG is formed in the Ge at the heterointerface. The mobility at T = 4.2K in a sample with an undoped alloy spacer layer of 4 nm was micro H = 3200 sq. cm./V-sec and in other samples was found to decrease with spacer layer thickness. Shubnikov-de Haas oscillations were observed at T = 1.5K with the magnetic field normal to the interface, but not with the field parallel to it. The oscillation period yields a surface charge density of 2 x 10 to the 12th/sq. cm. in reasonable agreement with the value of 3 x 10 to the 12th/sq. cm. obtained by Hall measurements. Silicon compounds, Germanium compounds. (mjm)