Mobility enhancement in undoped Ge 0.92 Sn 0.08 quantum well p-channel metal-oxide-semiconductor field-effect transistor fabricated on (111)-oriented substrate

We report the dependence of the electrical performance on surface orientations of undoped Ge 0.92 Sn 0.08 quantum well (QW) pMOSFETs on Ge(111) and (001) substrates. (111)-oriented Ge 0.92 Sn 0.08 QW pMOSFETs show a peak μ eff of 845 cm 2 V −1 s −1 and demonstrate a μ eff improvement of 25% over (001)-oriented control at an inversion charge density of 5 × 10 12 cm −2 . We also report that undoped Ge 0.92 Sn 0.08 QW pMOSFETs show a higher μ eff than the doped GeSn devices reported in the literature. The high μ eff achieved in undoped QW devices is enabled by incorporating high biaxial compressive strain (1.43%) and eliminating dopant impurity scattering in the defect-free channel.