9321826 Kahn Technical abstract: This study will focus on the structural, chemical, and electronic properties of surfaces and metal interfaces of wide band gap zinc-selenide and III-V nitrides (gallium nitride, indium nitride, aluminum nitride). The validity of the Schottky barrier models developed for narrower gap semiconductors will be tested for these materials. The nature of electronic surface states, their impact on the surface band bending and their role in the formation of metal-semiconductor barriers will be determined. The project will also investigate the occurrence of negative electron affinity which has been reported for aluminum nitride surfaces. Formation of metal-zinc-selenide and metal-nitride barriers will be investigated in order to establish the limits of the dependence of Schottky barriers on these materials. The thermal stability of interfaces, especially important for high temperature applications (gallium nitride) will be investigated. This will include a search for diffusion and chemical reaction barriers (e. g., titanium-gallium nitride). Finally, the difficult problem of making ohmic contacts to these p- doped semiconductors will be addressed. These contacts are crucial for the development of light emitting devices. Two techniques will be studied: combination of high p-doping and large work function metal (platinum) for p-gallium nitride, and high electronegativity polymeric and metallic (poly sulfur nitride) contact on p-zinc- selenide. Non-technical abstract: This project will investigate the structural, chemical and electronic properties of interfaces of two important types of semiconductors: zinc selenide and the Group III-V nitrides (gallium nitride, indium nitride, and aluminum nitride), which have applications in optoelectronics (emission in the green-blue for the II-VIs, blue-ultraviolet for the nitrides) and high temperature electronics (nitrides). The proposed work will begin to establish for these materials a solid understanding of their interface properties for future technological developments, as well as to test the validity of interface concepts and metal-semiconductor barrier models developed for narrower gap semiconductors. The formation of ohmic contacts will be investigated, since these are crucial for the operation of high- performance, reliable, light-emitting devices. For example the chemical stability of these contacts will be modulated via preparation of diffusion barriers which should lead to interface engineering of these materials. ***
