Metal/Indium-Zinc Oxide Semiconductor Heterostructures: A Platform for Radio-Frequency Devices

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Non-Technical Description: Semiconducting materials are an essential component of all modern electronics. In recent years, a new class of amorphous oxide based semiconducting materials has emerged. These materials are unique in that they can be deposited at room temperature on many solid surfaces while maintaining good electrical properties. The first application of such amorphous metal oxides has been in flat panel displays. The aim of this research project is to explore the fundamental materials science of miniaturized amorphous oxide devices integrated with new types of dielectric oxides. The structures can be made near room temperature and may enable an entirely new approach to design of electronic devices operating at radio frequencies for potential applications ranging from cell phones to satellites. Further, the combination of fundamental materials science and prototype device fabrication has educational impacts in and out of the classroom at Brown University. For instance, the low-cost, low-temperature amorphous oxide technology makes it ideal for a prototype fabrication lab in an undergraduate course on electronic materials and devices.Technical Description: Indium zinc oxide (IZO) in the amorphous form can be deposited at room temperature and achieve a high charge carrier density. This control over charge carrier density during and after deposition, combined with high mobilities, arbitrary substrate compatibility, easy regrowth and low-temperature in-situ oxidation for doping control and dielectric formation, makes these materials a promising platform for integration-ready high-current radio-frequency transistors. In this project, researchers examine the kinetics, electronic properties, and interface structure of metal/IZO formed by an in-situ self-limiting interface reaction. The goal is to achieve localized controllable ultra-high doping and self-limiting dielectric formation. The fundamental materials science knowledge obtained on reacted metal (Ti, Al) oxide/IZO interface structures is applicable to the fabrication of prototype transistors, particularly IZO-based high-current radio-frequency devices. Several critical materials challenges are low-resistance metal/IZO contacts, high and stable carrier density channels, and integration of materials with high dielectric constants. To tackle these challenges, thermodynamic/kinetic modeling of interface stability is combined with analytical techniques ranging from high-resolution transmission electron microscopy, glancing incidence angle x-ray diffraction, to interface electronic characterization techniques.