Fabrication of strain-controlled SiGe/Ge MODFET with ultrahigh hole mobility

The fabrication and characterization of a strain-controlled SiGe/Ge MODFET is described in detail. The heterostructure consisting of p-Si/sub 0.5/Ge/sub 0.5//Ge/Si/sub 1-xs/Ge/sub xs/ was grown by molecular beam epitaxy, and to enlarge the valence-band discontinuity, the strain in the p-Si/sub 0.5/Ge/sub 0.5//Ge layers was controlled by changing the composition of the relaxed Si/sub 1-xs/Ge/sub xs/ layer. A maximum hole mobility of about 9000 cm/sup 2//Vs was obtained at temperatures near 77 K. Some remaining problems, that muse be solved in order to make high performance MODFET's operating at room temperature, are also discussed.<
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