High quality Si/Si1minus;xGex/Siphyphen;type modulationhyphen;doped double heterostructures withx=0.12 and 0.15 have been grown by the ultrahigh vacuum/chemical vapor deposition technique. Hole mobilities as high as sim;3700 cm2/Vthinsp;s at 14 K have been obtained for heterostructures withx=0.12, at a sheet carrier concentration of sim;8times;1011cmminus;2. This is the highest hole mobility ever reported forphyphen;type Si material at these carrier concentrations. The electrical properties of these heterostructures at low temperatures are those expected of a twohyphen;dimensional hole gas at Si/SiGe and SiGe/Si heterointerfaces. The high hole mobility is indicative of excellent interfacial properties. Peak mobilities were observed to depend on the level and proximity of remote B dopant species, as well as the Ge content of the alloyed layers.
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