Elimination of parasitic channels in strained-Si p-channel metal-oxide-semiconductor field-effect transistors

Strained-Si p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) were fabricated on strained-Si/relaxed-Si0.7Ge0.3 heterostructures grown using molecular-beam epitaxy. Device simulation suggested that parasitic conduction through the Si0.7Ge0.3 layer can be eliminated by adding a proper concentration of impurity (>1017 cm-3) near the interface between the Si and the Si0.7Ge0.3 layers. The switching characteristics of fabricated devices were improved by increasing the impurity density to 1.6×1017 cm-3 suggesting that the formation of parasitic channels can be eliminated by channel doping in state-of-the-art short-channel MOSFETs (> 1×1018 cm-3). Effective hole mobility in our best strained-Si p-MOSFET was 30% higher than the universal value for conventional p-MOSFETs.

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