CdTe and ZnTe metal interface formation and Fermi-level pinning

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Abstract
Interfacial morphology and Fermi‐level pinning behavior at the interfaces of Al,Ag, and Pt with UHV‐cleaved CdTe and ZnTe have been studied using x‐ray photoelectron and ultraviolet photoemissionspectroscopies. Results are compared to metal/HgCdTe interface formation, where the weak Hg–Te bond and consequent ease of Hg loss strongly influence semiconductor disruption and metal–semiconductor intermixing. For Al/CdTe, we observe a case where the strong Al–Te reaction yields a significantly more extensive Al–Te reacted region than has been observed for HgCdTe. The Al/ZnTe interface is observed to be more abrupt than Al/CdTe. The final Fermi‐level pinning positions E fi=E f −E vbm for Al,Ag, and Pt on p‐type CdTe and p‐ZnTe have been determined. E fi is found to be roughly the same for both CdTe and ZnTe, with the value for ZnTe lying ∼0.2 eV closer to the valence‐band maximum for all three metals. From these results, one would expect Schottky barriers of about the same height for these metals on p‐CdTe and p‐ZnTe; and also that, in principle, metal interfaces with the two alloys HgCdTe and HgZnTe would have the same properties. Comparisons and implications for electrical behavior of metal contacts to the alloys are discussed.

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