Diamond-shaped Ge and Ge0.9Si0.1 gate-all-around nanowire FETs with four {111} facets by dry etch technology

We propose a feasible pathway to scale the Ge MOSFET technology by using a novel diamond-shaped Ge and Ge₀₉Si₀₁ gate-all-around (GAA) nanowire (NW) FETs with four {111} facets. The device fabrication requires only simple top-down dry etching and blanket Ge epitaxy techniques readily available in mass production. The proposed dry etching process involves three isotropic/anisotropic etching steps with different Cl₂/HBr ratios for forming the suspended diamond-shaped channel. Taking advantages of the GAA configuration, favorable carrier mobility of the {111} surface, nearly defect-free suspended channel, and improved dopant activation by incorporating Si, nFET and pFET with excellent performance have been demonstrated, including an I_on/I_off ratio exceeding 10⁸, the highest ever reported for Ge-based pFETs.