Germanium Nanowire Metal–Oxide–Semiconductor Field-Effect Transistor Fabricated by Complementary-Metal–Oxide–Semiconductor-Compatible Process

This work presents a complementary metal-oxide-semiconductor-compatible top-down fabrication of Ge nanowires along with their integration into pMOSFETs with "HfO₂/TaN" high-k/metal gate stacks. Lateral Ge wires down to 14 nm in diameter are achieved using a two-step dry etch process on a high-quality epitaxial Ge layer. To improve the interface quality between the Ge nanowire and the HfO₂, thermally grown GeO₂ and epitaxial-Si shells are used as interlayers. Devices with a GeO₂ shell demonstrated excellent I_ON/I_OFF ratios (>; 10⁶), whereas the epitaxial-Si shell was found to improve the field-effect mobility of the holes in Ge nanowires to 254 cm²V^-1 · s^-1.