Growth studies on Si0.8Ge0.2channel twohyphen;dimensional hole gases

摘要

We report a study of the influences of MBE conditions on the lowhyphen;temperature mobilities of Si/Si0.8Ge0.22DHG structures. A significant dependence of 2DHG mobility on growth temperature is observed with the maximum mobility of 3640 cm2thinsp;Vminus;1thinsp;sminus;1at 5.4 K being achieved at the relatively highhyphen;growth temperature of 640thinsp;deg;C. This dependence is associated with a reduction in interface charge density. Studies on lower mobility samples show that Cu contamination can be reduced both by growth interruptions and by modifications to the Ge source; this reduction produces improvements in the lowhyphen;temperature mobilities. We suggest that interface charge deriving from residual metal contamination is currently limiting the 4hyphen;K mobility. thinsp;