Contact Formation to Gallium Nitride: Interfacial Chemistry, Structure and Properties

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This GOALI project represents a collaborative effort between researchers at the U. of Wisconsin and Hewlett-Packard Laboratories to address fundamental materials science issues in ohmic contacts to GaN. The project takes a comprehensive approach to study basic issues concerning the thermodynamic and kinetic stability at metal/GaN interfaces as well as the transport behavior for both n- and p-type GaN. Extensive electrical and metallurgical characterization will be performed on annealed metal/GaN contacts fabricated using selected metallizations as model systems. The electrical characterization will include current-voltage (I-V) and capacitance-voltage (C-V) measurements to determine such properties as the specific contact resistance, the magnitude of the Schottky or contact barrier height, and the changes in the space charge region near the surface. Metallurgical characterization of the reacted interfaces will be performed using a variety of techniques such as SAM, XRD, TEM, HRTEM, SIMS and RBS. To address initial stages of contact formation, the evolution of interfaces will be examined by x-ray photoemission spectroscopy (XPS), utilizing synchrotron radiation. The XPS-based studies on metal/GaN will complement the more extensive characterization of the bulk thin films. The combined studies are expected to provide insight into metal/GaN interfaces not currently available and furnish information critical for development of metallizations to nitride based semiconductor devices.%%%The project addresses basic research issues in a topical area of materials science having high potential technological relevance. The research will contribute basic materials science knowledge at a fundamental level to important fabrication aspects of electronic/photonic devices. New experimental materials science and optical tools are now available to allow more detailed observation of elementary surface/interface processes which when better understood allow advances in fundamental science and technology. The basic knowledge and understanding gained from the research is expected to contribute to improving the performance and stability of advanced devices and circuits for computing and communications. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. The project is co-supported by the DMR/Electronic Materials program and the MPS OMA(Office of Multidisciplinary Activities).***