Reduction of Schottky barrier height at metal/n-Ge interface by introducing an ultra-high Sn content Ge1-xSnx interlayer.

We investigated the impact of introducing an ultra-high Sn content Ge_1-xSn_x interlayer on the electrical properties at the metal/Ge interface. We achieved epitaxial growth of a Ge_1-xSn_x thin layer with an ultra-high substitutional Sn content of up to 46% on a Ge(001) substrate by considering the misfit strain between Ge_1-xSn_x and Ge. From the current-voltage characteristics of Al/ Ge_1-xSn_x/n-Ge Schottky diodes, we found an increase in the forward current density of the thermionic emission current with increasing Sn content in the Ge_1-xSn_x interlayer. The Schottky barrier height estimated in Al/Ge_1-xSn_x/n-Ge diodes decreases to 0.49 eV with an increase in the Sn content up to 46% of the Ge_1-xSn_x interlayer. The reduction of the barrier height may be due to the shift of the Fermi level pinning position at the metal/Ge interface with a Ge_1-xSn_x interlayer whose valence band edge is higher than that of Ge. This result enables the effective reduction of the contact resistivity by introducing a group-IV semiconductor alloy interlayer of Ge_1-xSn_x into the metal/n-Ge interface. [ABSTRACT FROM AUTHOR]