New findings on the scattering mechanisms in inversion layers of Ge (111), (110), and (100) nMOSFETs under high electric field—Differences with Si nMOSFETs

We have, for the first time, confirmed that in Ge nMOSFETs the dominant scattering mechanism in the high-field region is not necessarily the surface roughness scattering. We found that, in Ge(100) nMOSFETs, because the phonon scattering is still dominant in the high-field region, it is difficult to enhance the high-field mobility by controlling the interface roughness. Since Ge(111) and Ge(110) nMOSFETs are free of the intervalley phonon scattering, the high-field mobility could be enhanced by the Ge interface engineering. Furthermore, different from that in Si nMOSFETs, surface roughness scattering in Ge nMOSFETs shows a strong temperature dependence.