Impacts of ITO interlayer thickness on metal/n-Ge contacts

- A thin ITO layer was formed by magnetron sputtering.
- The SBH is greatly affected by the thickness of ITO for metal/ITO/n-Ge contacts.
- ITO has a wide range of thicknesses (4-50 nm) to retain ohmic contact.
- The SBHs are independent on work functions of cap metals.
- An interdiffusion model was proposed to explain the modulation of SBH

The dependence of Schottky barrier height (SBH) of metal/ITO/n-Ge contacts on ITO interlayer thickness is experimentally investigated. The SBH of metal/ITO/n-Ge contacts for various metal electrodes of Al, Cu, and Pt is estimated. It is found that the SBH of metal/ITO/n-Ge contacts decreases with increase of ITO thickness from 0 to 4 nm, and the dependence of SBH on the metal work function is weak. When the thickness of ITO is larger than 4 nm, ohmic metal/ITO/n-Ge contacts are obtained for different metal electrode. The formation of ohmic contact can be ascribed to high carrier concentration of ITO itself and the excellent passivation for Ge surface. The interdiffusion between cap metal and ITO should be responsible for the modulation of SBH of metal/ITO/n-Ge contacts.

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