Evidence of Si∕SiGe heterojunction roughness scattering

Abstract

The separation distance between the electron channel at oxide∕Si interface and the strained-Si∕relaxed-SiGe heterojunction can significantly affect the effective electron mobility of metal–oxide–silicon field-effect transistors due to the roughness scattering of the underneath Si∕SiGe heterojunction. The mobility degradation due to the Si∕SiGe heterojunction with the roughness of 7 nm becomes insignificant when the strained-Si thickness is larger than ∼20nm. A clear hole confinement shoulder is observed in the accumulation region of the capacitance–voltage curves, indicating that the abrupt transition from the SiGe buffer to strained Si is maintained at the rough heterojunction. The heterojunction roughness scattering not only degrades the electron mobility, but also degrades the device characteristics such as the transconductance and cut-off frequency.

Studying the impact of carbon on device performance for strained-Si MOSFETs

“…However, this has many disadvantages such as higher surface roughness, lower thermal budget, a thicker buffer layer, and higher cost [2][3][4]. The thicker SiGe buffer is required as the increase in Ge content leads to an increase in the growth cycle and lower throughput.…”