High hole mobility in Si/Si1−xGex/Si p-type modulation-doped double heterostructures

High quality Si/Si1−xGex/Si p-type modulation-doped double heterostructures with x=0.12 and 0.15 have been grown by the ultrahigh vacuum/chemical vapor deposition technique. Hole mobilities as high as ∼3700 cm2/V s at 14 K have been obtained for heterostructures with x=0.12, at a sheet carrier concentration of ∼8×1011 cm−2. This is the highest hole mobility ever reported for p-type Si material at these carrier concentrations. The electrical properties of these heterostructures at low temperatures are those expected of a two-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.