Strained Germanium Quantum Well PMOSFETs on SOI with Mobility Enhancement by External Uniaxial Stress

Abstract

Well-behaved Ge quantum well (QW) p-channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) were fabricated on silicon-on-insulator (SOI) substrate. By optimizing the growth conditions, ultrathin fully strained Ge film was directly epitaxially grown on SOI at about 450 °C using ultra-high vacuum chemical vapor deposition. In situ Si2H6 passivation of Ge was utilized to form a high-quality SiO2/Si interfacial layer between the high-κ dielectric and channels. Strained Ge QW pMOSFETs achieve the significantly improved effective hole mobility μeff as compared with the relaxed Si and Ge control devices. At an inversion charge density of Qinv of 2 × 1012 cm−2, Ge QW pMOSFETs on SOI exhibit a 104% μeff enhancement over relaxed Ge control transistors. It is also demonstrated that μeff of Ge pMOSFETs on SOI can be further boosted by applying an external uniaxial compressive strain.