Epitaxial formation and electrical properties of Ni germanide/Ge(110) contacts

We have investigated the epitaxial formation and electrical properties of Ni germanide/Ge(110) contacts. X-ray diffraction and transmission electron microscopy measurements have revealed that Ni₅Ge₃ and NiGe layers are epitaxially formed on a Ge(110) substrate after annealing at 200–350 °C. An epitaxial Ni₅Ge₃ layer is formed after annealing with the relationships Ni₅Ge₃(001)//Ge(110) and Ni₅Ge₃[311]//Ge[001]. We found that the orientation relationship between an epitaxial NiGe layer and Ge(110) substrate depends on the annealing temperature. When annealed at 300–350 °C, the orientation relationship is NiGe(100)//Ge(110) and NiGe[001]//Ge[001], while at 200–230 °C, the relationship is NiGe(102)//Ge(110) and NiGe[010]//Ge[001]. We demonstrate that the Schottky barrier height of the epitaxial NiGe(100)/Ge(110) contact is as low as 0.44 eV, as estimated from the current density–voltage characteristics, while that of polycrystalline NiGe/Ge(001) is 0.55 eV. - Highlights: • We report the epitaxial formation and electrical property of NiGe/Ge(110) contact. • Two kinds of epitaxial NiGe layers with different orientations were obtained. • Epitaxial NiGe/Ge(110) has lower Schottky barrier height than that of NiGe/Ge(001)