CAREER: Minority Carrier Transport in Wide Bandgap Semiconductor Nanowires: Classical and Quantum Size Effects

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Technical: This project is to study minority carrier transport properties in nanowires made of wide-bandgap semiconductors. Minority carrier transport is of special interest and importance, as it controls majority carrier transport in many devices and is also sensitive to carrier-carrier interactions. In this project, free-standing wide-bandgap semiconductor nanowires with controlled dimensions are synthesized using the vapor-liquid-solid growth method. One-dimensional minority carrier transport, specifically the surface-dependent and -independent minority carrier diffusion lengths and drift mobilities, is studied using novel scanning probe microscopy-based techniques with integrated electrical and optical probing capabilities. The classical size effects are investigated via the correlation between surface electronic structures under various surface conditions and effects of surfaces as minority carrier recombination and scattering centers. The quantum size effects are examined via the size (diameter) dependence of the minority carrier mobility controlled by various transport-limiting mechanisms including carrier-impurity, carrier-phonon, and carrier-carrier (minority-majority) scattering processes.Non-technical: The project addresses basic research issues in a topical area of materials science with high technological relevance. With the importance of carrier transport in wide-ranging electronic and optoelectronic applications, the success of this project will provide a fundamental basis for the potentially transformative nanoscale materials and device engineering efforts. This project will lay the foundation for future efforts by the PI to develop the approach of tuning the interplay among electrons, phonons, photons, impurities, and surfaces via dimension, surface, and impurity engineering in order to achieve an integrated control over optical, electrical, magnetic, and thermoelectric properties in nanoscale materials. The research component of this project is integrated into multifaceted educational and outreach activities. In addition to providing research training for students at both undergraduate and graduate levels, the educational efforts aim to enhance general undergraduate physics education for students with diverse backgrounds, as well as to provide a "focused concept" laboratory experience for undergraduate physics majors at the Washington State University. The outreach element of this project aims to provide continuing, long-term support for science teacher education and professional development.