Effect of Hydrogen Annealing on Contact Resistance Reduction of Metal-Interlayer-n-Germanium Source/Drain Structure

The effect of post-deposition H₂ annealing (PDHA) on the reduction of a contact resistance by the metal-interlayer-semiconductor (M-I-S) source/drain (S/D) structure of the germanium (Ge) n-channel field-effect transistor (FET) is demonstrated in this letter. The M-I-S structure reduces the contact resistance of the metal/n-type Ge (n-Ge) contact by alleviating the Fermi-level pinning (FLP). In addition, the PDHA induces interlayer doping and interface controlling effects that result in a reduction of the tunneling resistance and the series resistance regarding the interlayer and an alleviation of the FLP, respectively. A specific contact resistivity ( ρc) of 3.4 × 10^-4 Ω · cm² was achieved on a moderately doped n-Ge substrate (1 × 10¹⁷ cm ^-3) , whereby 5900× reduction was exhibited from the Ti/n-Ge structure, and a 10× reduction was achieved from the Ti/Ar plasma-treated TiO_2-x/n-Ge structure. The PDHA technique is, therefore, presented as a promising S/D contact technique for the development of the Ge n-channel FET, as it can further lower the contact resistance of the M-I-S structure.