Electron Mobility Enhancement in GeSn n-Channel MOSFETs by Tensile Strain

A record high electron mobility of 698 cm
²
/V·s in a tensile-strainedGe
_0.96
Sn
_0.04
nMOSFET is demonstrated in this letter. High-quality GeSn films were epitaxially grown by low-temperature chemical vapor deposition. Different strain conditions in the active GeSn layers were achieved by Ge or GeSn relaxed buffers. A mesa FET structure was used to effectively reduce the OFF leakage by a recessed p/n junction in Ge. The ION/IOFF ratio in the mesa GeSn FETs is boosted by a factor of 100 compared to conventional planar devices. As the GeSn film becomes more tensile strained, the channel mobility is enhanced, which could be attributed to a higher carrier population in the Γ valley.