The Schottky-barrier energy φB for Al, Ni, Pd, Co, Au, and Ag contacts on chemically etched 〈100〉 surfaces of both p- and n-type InP was measured and the metallurgical behavior of the contact structures was studied using Auger-electron spectroscopy. No simple linear relationship could be found between the measured Schottky barrier energies on InP and the work functions or the electronegativities of the contact metals. Therefore, the results could not be explained in terms of the traditional Schottky and Bardeen theories. However, a very well defined relationship was observed between the Schottky barrier energies and the heats of reaction per formula unit ΔHr for the most stable metal phosphides that could be formed between the contact metals and the InP substrate. The contact metals Au and Ag whose phosphides are less stable than InP (i.e., ΔHr >0) produced diffuse interfaces, characterized by extensive outdiffusion of In, and yielded low values of φBp, the Schottky-barrier energy on p-type InP; whereas the contact metals Al and Ni which can form compounds with phosphorus that are significantly more stable than InP (i.e., ΔHr <0) showed less In outdiffusion and produced higher values of φBp. Two distinct Fermi-level pinning positions located at 0.50±0.01 eV and 0.40±0.02 eV below the conduction band minimum of InP were found and correlated to the metallurgical state of the contact structures. The findings of the present study strongly suggest that Schottky-barrier formation on InP is controlled by chemical reaction between the contact metal and the InP substrate, with the degree of chemical reactivity appearing to determine the Fermi-level pinning position at the interface.
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Hökelek et al. (1983) studied this question.