Electron Mobility Enhancement in GeSn n-Channel MOSFETs by Tensile Strain
Yen Chuang, Chia-You Liu, Guang-Li Luo, Jiun‐Yun Li
Abstract
A record high electron mobility of 698 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /V·s in a tensile-strainedGe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.96</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.04</sub> 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.