First Experimental Observation of Channel Thickness Scaling Induced Electron Mobility Enhancement in UTB-GeOI nMOSFETs

High quality ultrathin body (UTB)-Ge-on-insulator (GeOI) substrates have been fabricated with advanced layer transfer technology called HEtero-Layer-Lift-Off. With precise control of interfacial qualities, Ge crystallinity and thickness fluctuation in GeOI substrates, electron mobility of UTB-GeOI nMOSFETs with body thickness (
$T_{\text {body}}$
) from 20 to 3 nm has been systematically investigated. A significant electron mobility enhancement as
$T_{\text {body}}$
scaling below 13 nm has been observed. This newly found mobility enhancement induced by channel thickness scaling could be attributed to the modulation of energy band structure in (001) confined UTB GeOI, where electron effective mass reduction is predicted by first-principle calculation.