Surface Passivation of Germanium Using SF6 Plasma to Reduce Source/Drain Contact Resistance in Germanium n-FET

We demonstrate Fermi-level unpinning and contact resistance reduction by surface passivation using SF6plasma treatment of a metal/germanium (Ge) contact. A specific contact resistivity (Pc) of 1.14 × 10-3Ω · cm2and 0.31 eV of Schottky barrier height is achieved for a Ti/SF6-treated n-type Ge (n-Ge) (Nd = 1 × 1017cm-3) contact, exhibiting 1700 times Pc reduction from a Ti/nontreated n-Ge contact. A convenient and effective passivation process of the Ge surface is presented to alleviate Fermi-level pinning at metal/Ge contact and lower source/drain contact resistance of Ge n-type field-effect transistors.