A Study of the Schottky-Barrier Height of Nickel Germanosilicide Contacts Formed on $\hbox{Si}_{1-x}\hbox{Ge}_{x}$ Epilayer on Si Substrates
Formation and electrical properties of nickel silicidized n-type Si and <formula formulatype="inline"><tex Notation="TeX">$ \hbox{Si}_{1-x}\hbox{Ge}_{x}$</tex></formula> epilayers on a Si substrate are comparatively studied. The improvement of thermal stability of germanosilicide can be attributed to the thicker NiSi(Ge) film and the delay of phase transformation with Ge incorporation, as well as the reduction in interface energy with Ge segregation at the interface. The Schottky-barrier heights (SBHs) of the contacts formed by sputtering Ni on the strained <formula formulatype="inline"><tex Notation="TeX">$\hbox{Si}_{1-x}\hbox{Ge}_{x}$</tex></formula> (<formula formulatype="inline"> <tex Notation="TeX">$x = \hbox{0.07}$</tex></formula> and 0.2) epilayers significantly increase after germanosilicidation and with increasing annealing temperature, markedly contrasting to the quick drop of SBH of the silicidized Si contact made by the same process. The raise of SBH of the <formula formulatype="inline"><tex Notation="TeX">$\hbox{Ni/Si}_{1-x}\hbox{Ge}_{x}$ </tex></formula> contact after germanosilicidation and with increasing annealing temperature is dominated by a Fermi-level pinning effect due to Ge segregation at the interface and the generation of dislocations driven by strain relaxation in the <formula formulatype="inline"><tex Notation="TeX">$\hbox{Si}_{1-x}\hbox{Ge}_{x}$</tex></formula> epilayers, rather than the reduction in work function when Ni transforms to NiSiGe during the germanosilicidation process.