Formation and characterization of Ni/Al Ohmic contact on n+-type GeSn

•A Ni/Al Ohmic contact was obtained on a highly doped n-type GeSn.•The specific contact resistivity was as low as (2.26 ± 0.11) × 10−4 Ω cm2.•The formation of the Ni(GeSn) phase with low resistance contributes to the result.•High doping narrowing the Schottky barrier increases the quantum tunneling current.

In this study, a Ni/Al Ohmic contact on a highly doped n-type GeSn has been investigated. A specific contact resistivity as low as (2.26 ± 0.11) × 10−4 Ω cm2 was obtained with the GeSn sample annealed at a temperature of 450 °C for 30 s. The linear Ohmic behavior was attributed to the low resistance of the Ni(GeSn) phase; this behavior was determined using glancing-angle X-ray diffraction, and the quantum tunneling current through the Schottky barrier narrowed because of high doping; this phenomenon was confirmed from the contact resistance characteristics at different temperatures from 45 to 205 K.