Effect of strain in Si/SiGe modulation-doped quantum wells

A novel technique has been devised to allow the growth of strained Si/SiGe quantum wells (QW's) on Si substrates, while virtually eliminating threading dislocations. The amount of strain in the quantum wells is tuned by ramping the Ge content in a Si/SiGe multilayer buffer. Both n-type and p-type modulation-doped structures have been grown using this technique, with mobilities at 1.4 K as high as 19 000 cm2/V s and 6000 cm2/V s, respectively. The effect of strain on the bandstructure in both cases is investigated. © 1992.