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Research
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Innovations in semiconductor materials have enabled many recent advances
in technology from cell phones to flat panel displays to solid state
lighting to solar electricity. All of these applications make use of thin
layers of semiconductors on the order of a micron thick and most require
semiconductors that are crystalline and aligned with a single crystal
substrate. There are great opportunities for further advances in
semiconductor materials and new physical phenomena, as well as important
unmet needs for new technology. We are exploring the growth of III-V
compound semiconductors and oxide materials on single crystal substrates
using molecular beam epitaxy ("MBE"), and studying their electronic and
optical properties. MBE is a method for growing thin crystalline layers in
high vacuum using beams of atoms produced by heated effusion cells. The
atom fluxes can be controlled with mechanical shutters so that only a
fraction of an atomic layer is deposited at a time. By assembling
materials from beams of atoms on a temperature-controlled single-crystal
template we are able to make novel metastable materials, that have new and
useful properties, that cannot be made in bulk form. In the self-assembly
process that occurs during crystal growth by vapour deposition of atoms
onto a surface, characteristic macroscopic patterns develop as the
thickness of the deposited layer grows. These macroscopic patterns develop
from atomic scale phenomena and can in some cases be described
mathematically. A primary focus of our program is the growth of III-V
compound semiconductors and rare earth doped oxides for light emitting
devices for medical diagnostics and therapy.
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