Fabrication of Highly n-Type-Doped Germanium Nanowires and Ohmic Contacts Using Ion Implantation and Flash Lamp Annealing

Accurate control of doping and fabrication of metal contacts on n-type germanium nanowires (GeNWs) with low resistance and linear characteristics remain a major challenge in germanium-based nanoelectronics. Here, we present a combined approach to fabricate Ohmic contacts on n-type-doped GeNWs. Phosphorus (P) implantation, followed by millisecond rear-side flash lamp annealing, was used to produce highly n-type-doped Ge with an electron concentration in the order of 1019–1020 cm–3. Electron beam lithography, inductively coupled plasma reactive ion etching, and nickel (Ni) deposition were used to fabricate GeNW-based devices with a symmetric Hall bar configuration, which allows detailed electrical characterization of the NWs. Afterward, rear-side flash lamp annealing was applied to form Ni germanide at the Ni-GeNW contacts to reduce the Schottky barrier height. The two-probe current–voltage measurements on n-type-doped GeNWs exhibit linear Ohmic behavior. Also, the size-dependent electrical measurements showed that carrier scattering near the NW surfaces and reduction of the effective NW cross-section dominate the charge transport in the GeNWs.