Comparative investigation of Schottky barrier height of Ni/n-type Ge and Ni/n-type GeSn

We report an investigation of the Schottky barrier height (SBH) of Ni/n-type Ge and Ni/n-type GeSn films that is annealed at a wide range of temperatures. Both voltage- and temperature-dependent current–voltage (I–V) measurements are performed. From the analysis of these nonlinear I–V traces, the SBH is found and the results shows that the SBH of Ni/n-type GeSn (a) is smaller than that of Ni/n-type Ge and (b) decreases with the Sn content of the surface GeSn layer associated with the thermal annealing. By modeling the composition- and strain-dependent energy bandgap (Eg), the relationship between the SBH and Eg is established and it is found that SBH/Eg ∼0.8. These results suggest that the GeSn film could serve as an interfacial layer for the reduction of the SBH in Ge-based electronic devices that are desirable for applications.