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

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 μ _eff as compared with the relaxed Si and Ge control devices. At an inversion charge density of Q _inv of 2 × 10¹² cm^-2, Ge QW pMOSFETs on SOI exhibit a 104% μ _eff enhancement over relaxed Ge control transistors. It is also demonstrated that μ _eff of Ge pMOSFETs on SOI can be further boosted by applying an external uniaxial compressive strain.