On the High-Field Transport and Uniaxial Stress Effect in Ge PFETs

Ge is one of the promising candidates for high-mobility channel material in future complementary metal-oxide-semiconductor technology. High-field transport in short-channel Ge p-channel field-effect transistors (PFETs) needs to be examined since device performance is determined by high-field velocity in quasi-ballistic transport regime. In this paper, ballisticity and the relationship between carrier velocity and mobility in short-channel (70-nm) Ge PFETs were thoroughly investigated. A 1.6 × -2× higher velocity was confirmed in Ge PFETs than that in Si PFETs. Uniaxial stress is also a strong performance booster besides high-mobility substrate. The effectiveness of the uniaxial stress to velocity enhancement in Ge PFETs was experimentally demonstrated in short channel regime. A 1.4× higher drive current can be achievable by uniaxially strained Ge PFET in ballistic transport regime as compared with strained Si PFET.