Fundamental and Practical Studies of Metal Contacts on Mercury Zinc Telluride.

摘要

How the metal overlayer grows and chemically interacts with the substrate in metal/II-VI systems such as Cadmium Telluride and Zinc Telluride has practical importance for the electrical characteristics of metal contacts to these materials. By studying metal interfaces with these binaries, we gain insight into the role of the weak Mercury-bonding in the alloys Mercury Cadmium Telluride and Mercury Zinc Telluride during metal contact formation, where severe Hg depletion on the order of 20-60% from the top few layers of the HgCdTe substrate is typically observed upon metal deposition. We report results of our comparative study of the interfacial chemistry and band bending behavior for Aluminum, Indium, Silver, and Platinum overlayers on vacuum-cleaved (p)-CdTe and (p)-ZnTe(110) using both UPS and XPS. A range of metal-substrate reactivities have been considered: Al reacts strongly with Tellurium, Ag moderately, and In minimally, with no evidence seen for In reaction on ZnTe. Pt exhibits strong alloying behavior with both Cd and Zn. We compare these results for the binaries to metal/HgCdTe interface formation. We find that Hg loss can significantly influence the extent of reaction and/or intermixing for these overlayers, with resulting disruption either inhibiting or facilitating chemical interaction. We consider band bending at these metal/CdTe and metal/ZnTe interfaces to correlate Fermi level movement in the bandgap during metal deposition with interfacial chemistry and morphology of the overlayer. Keywords: Schottky barriers. (aw)