$\hbox{Ni}(\hbox{Ge}_{1 - x}\hbox{Sn}_{x})$ Ohmic Contact Formation on N-Type $\hbox{Ge}_{1 - x}\hbox{Sn}_{x}$ Using Selenium or Sulfur Implant and Segregation

The physics of ohmic contact formation for nickel stanogermanide [ Ni(Ge
_1-x
Sn
_x
)] on n-type germanium-tin (n-Ge
_1-x
Sn
_x
) was investigated. Low-resistivity Ni(Ge
_1-x
Sn
_x
) was formed on Ge
_1-x
Sn
_x
using a 350 °C 30-s anneal. Ion implantation of selenium (Se) or sulfur (S) into n-Ge
_1-x
Sn
_x
followed by nickel stanogermanidation led to the segregation of Se or S at the Ni(Ge
_1-x
Sn
_x
)/n-Ge
_1-x
Sn
_x
interface. Low effective electron Schottky barrier height (Φ
Bn
) of 0.12 and 0.11 eV was achieved for Ni(Ge
_1-x
Sn
_x
)/n-Ge
_1-x
Sn
_x
contacts with Se and S segregation, respectively. A simulation study was also performed to explain the experimental observations. Se and S atoms could be modeled as donor-like traps near the Ni(Ge
_1-x
Sn
_x
)/n-Ge
_1-x
Sn
_x
interface, modifying the potential profile near the contact and giving rise to trap-assisted tunneling to increase the reverse leakage current for ohmic contact formation.