Impact of nitrogen plasma passivation on the Al/n-Ge contact

•A thin GeOxNy layer was formed by N2 plasma.•The principal parameters of N2 plasma treatment and additional post anneal have a great impact on the Al/n-Ge contact.•A model was proposed to explain the variation of Schottky barrier height.•The GeOxNy layer was also benefit to achieve a low leakage current density for HfO2/Ge MOS capacitors.

Severe Fermi level pinning at the interface of metal/n-Ge leads to the formation of a Schottky barrier. Therefore, a high contact resistance is introduced, debasing the performance of Ge devices. In this study, a Ge surface was treated by nitrogen plasma to form an ultra-thin Germanium oxynitride (GeOxNy) passivation layer. It was found that the Schottky barrier height (SBH) of metal/n-Ge contact was strongly modulated by the GeOxNy interlayer, indicating alleviation of Fermi-level pinning effect. By adjusting the principal parameters of N2 plasma treatment and additional post anneal, a Quasi-ohmic Al/n-Ge contact was achieved. Furthermore, the introduced GeOxNy layer gave extremely lower leakage current density of the gate stack for HfO2/Ge devices. These results demonstrate that GeOxNy formed by N2 plasma would be greatly beneficial to the fabrication of the Ge-based devices.