Electron mobility enhancement in strained SiGe vertical n -type metal–oxide–semiconductor field-effect transistors

We have fabricated strained SiGe vertical n-channel metal–oxide–semiconductor field-effect transistors (MOSFETs) by Ge ion implantation and solid phase epitaxy. No Si cap is needed in this process because Ge is implanted after gate oxide growth. The vertical MOSFETs are fabricated with a channel length below 0.2 μm without sophisticated lithography and the whole process is compatible with a regular complementary metal–oxide–semiconductor process. The drive current for these devices has been observed to be enhanced by 50% compared with Si control devices on the same wafer. Electron mobility enhancement in the out-of-plane direction for the strained SiGe layer was demonstrated in this study.