Comprehensive Study of Electron Mobility and Band Gap in Tensile-Strained Bulk Ge

In this study, electron mobility and band-gap energy in bulk Ge for arbitrary current directions under both biaxial and uniaxial tensile strains are thoroughly investigated by numerical calculations in order to identify the optimum strain configuration and channel direction. The results revealed a trade-off between a high electron mobility and a wide band gap. The maximum electron mobility of 5,680 cm 2 V -1 s -1 was obtained under isotropic biaxial tensile strain in the (111) plane, while the narrowest band gap of 0.436 eV was obtained. In order to study cases with more realistic strain configurations such as process-induced strain, electron mobility and band-gap energy under anisotropic biaxial and uniaxial strains were also studied. It was shown that a combination of the [110] channel direction with uniaxial tensile strain parallel to the channel provides the most technically preferable solution, realizing an electron mobility of 5,626 cm 2 V -1 s -1 and a band-gap energy of 0.512 eV.