Ge (100) and (111) N- and P-FETs With High Mobility and Low- $T$ Mobility Characterization

In this paper, we demonstrate high-mobility bulk Ge N- and P-FETs with GeON gate dielectric. The highest electron mobility to date in Ge is reported, and two times improvement over universal hole mobility is achieved for Ge P-FETs. For the first time, the effect of surface orientation on Ge mobility is investigated experimentally. A 50% improvement in electron mobility is shown for the (111) substrate orientation compared to the (100) orientation. Carrier scattering mechanisms are studied through low-temperature mobility measurements and interface characterization. The conductance technique is applied at low temperatures for complete mapping of the density of interface traps (D_it) across the Ge bandgap and also close to the band edges. Carrier scattering mechanisms and the distribution of D_it are compared for Ge NMOS and PMOS.