Schottky barrier formation at metal/n-ZnSe interfaces and characterization of Au/n-ZnSe by ballistic electron emission microscopy

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Abstract
Current transport and ballisticelectron emissionmicroscopy (BEEM) studies have been carried out on metal contacts fabricated on chemically etched n -ZnSe epitaxial layers grown by molecular beam epitaxy. The contact materials Ag, Sb, Au, Ge/Au, Sn, Ni, and Pd form one or more barrier heights out of the following seven discrete values: 0.90, 1.20, 1.32, 1.50, 1.67, 1.80, and 2.10±0.04 eV observed to date. BEEM work carried out on Au/n-ZnSe systems has identified four levels 1.32 [Morgan et al., J. Appl. Phys. 79, 1532 (1996)], 1.50, 1.67 [Coratger et al., Phys. Rev. B 15, 2357 (1995)] and 1.80 eV to date, confirming Fermi-level pinning at different positions. Schottky barrier formation at metal/ n -ZnSe systems cannot be explained by the simple Schottky model. The strong Fermi-level pinning observed could be due to bulk and/or surface defects of the ZnSe material.