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

摘要

Strained--Si p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) were fabricated on strained--Si/relaxed-Si_0.7Ge_0.3 heterostructures grown using molecular-beam epitaxy. Device simulation suggested that parasitic conduction through the Si_0.7Ge_0.3 layer can be eliminated by adding a proper concentration of impurity (＞ 10~17 cm~-3) near the interface between the Si and the Si_0.7Ge_0.3 layers. The switching characteristics of fabricated devices were improved by increasing the impurity density to 1.6 × 10~17 cm~-3 suggesting that the formation of parasitic channels can be eliminated by channel doping in state-of the-art short--channel MOSFETs (＞l × 10~18 cm~-3). Effective hole mobility in our best strained-Si p--MOSFET was 30/100 higher than the universal value for conventional p-MOSFETs.