nstitution: McGill University
Department: Department of Electrical and Computer Engineering
PhD Supervisor: Dr. Z Mi
Application deadline: September 15, 2013
Funding Availability: Available if admitted
Project Title: Growth/synthesis, properties, and device applications of III-nitride nanowire structures

A PhD studentship is available to investigate the properties and device applications of III-nitride nanowire structures in the Nanoelectronics Group (http://people.mcgill.ca/zetian.mi/) at McGill University. The student will join a dynamic team, with special focus on the development of solar fuels and solid state lighting devices/systems using nanowire structures. Brief description of the research work follows.

Group III-nitride compound semiconductors exhibit unique electrical and optical properties, including high electron mobility, large saturation velocity, large electric breakdown field, extreme chemical stability, and direct energy bandgap encompassing the entire solar spectrum. Consequently, they have emerged as the materials of choice for ultraviolet and visible LEDs and lasers, high-power and high-temperature electronics, and future multi-junction solar cells, to name just a few. Due to the lack of native substrates, however, conventional III-nitride planar heterostructures generally exhibit very high densities of dislocations, which severely limit their performance and reliability. In this regard, one aspect of our research program is to investigate the epitaxial growth and characterization of III-nitride nanowire heterostructures, which can exhibit drastically reduced dislocation densities. This study, by designing materials at the atomic scale, promises an entirely new avenue for the development of silicon integrated nanowire electronic, photonic, and biochemical devices. Part of this project is also be related to the development of broadband InAlGaN nanowire heterostructures for both lighting and solar energy devices.

The device applications of III-nitride nanowire structures will be further investigated. Phosphor-free white LEDs, that can be fabricated on low cost, large area substrates and can display high luminous flux, hold immense promise for the emerging solid state lighting and full-color displays. Such devices can be realized monolithically by stacking blue, green and red emitters in a single epitaxial step. They can exhibit much higher quantum efficiency, better color rendering capability, and significantly reduced manufacturing cost and improved reliability, compared to the commercial phosphor-based white LEDs. In this regard, this project is also related to the development of III-nitride nanowire white LEDs, which can exhibit drastically reduced dislocation densities and polarization field and can provide a greater degree of flexibility for sophisticated device engineering, compared to conventional planar heterostructures.

We also seek to elucidate the properties and potential of metal nitride nanowires as building blocks for solar-hydrogen conversion devices. Detailed water splitting and hydrogen generation experiments will be performed on metal nitride nanowire arrays. We will investigate the role of surface states, polarity, and electronic structures on both H2 and O2 evolution, which will be compared with the reaction dynamics derived by atomistic total energy computational modeling based on the density functional theory and nudged elastic band methods, with the objective to establish the guiding principles for the water absorption, the generation of molecular hydrogen, and the water oxidation process on metal-nitride surfaces. The realization of wafer-level photocatalytic water splitting (compared to conventional powder based approaches) promises low cost, high performance, and compact hydrogen production systems that were not previously possible. This study will also lead to exciting discoveries in low dimensional physics, nanomaterials, and photochemistry, and will have broad impact on artificial photosynthesis and carbon-neutral energy.

The student will have full access to state-of-the-art molecular beam epitaxial growth, materials characterization, and device fabrication and measurement equipment. He/she will have ample opportunities to be trained and to gain expertise in materials growth/synthesis, device design, fabrication, and characterization, to system-level integration.

Details about the application process may be found at http://www.mcgill.ca/ece/admissions/graduate/process/apply. If interested, please email your CV and transcripts to zetian.mi@gmail.com before applying.