Electron mobility in Ge and strained-Si channel ultrathin-body metal-oxide semi conductor field-effect transistors

Electron mobility in strained silicon and various surface oriented germanium ultrathin-body (UTB) metal-oxide semiconductor field-effect transistors (MOSFETs) with sub-10-nm-body thickness are systematically studied. For biaxial tensile strained-Si UTB MOSFETs, strain effects offer mobility enhancement down to a body thickness of 3nm, below which strong quantum confinement effect renders further valley splitting via application of strain redundant. For Ge channel UTB MOSFETs, electron mobility is found to be highly dependent on surface orientation. Ge⟨100⟩ and Ge⟨110⟩ surfaces have low quantization mass that leads to a lower mobility than that of Si in aggressively scaled UTB MOSFETs.