Growth of gallium nitride nanowires by molecular beam eptiaxy
Abstract
Group III-nitride nanowires offer a novel route to enhanced device performance based on reduced dimensionality. Molecular beam epitaxy has been successfully employed to grow catalysis-free GaN nanowires. However one must still maintain control over nanowire density and cross-sectional shape if useful devices are to be made. This study seeks to determine the factors that promote uniform hexagonal-shaped nanowires for catalyst-free growth of GaN nanowires by MBE on the silicon (111) surface. The dependence of GaN nanowire shapes on growth time and temperature was explored. Two possible causes for the irregular shape formation may be due to the radial growth rate and nucleation rate. If the radial growth rate is too slow, there is insufficient time to grow out unstable facets. Merging of nanowires due to fast nucleation will also result in irregular nanowire shape formation. Under certain growth conditions, the GaN nanowire shapes will take on a hexagonal shape. The hexagonal shape does not vary too much with temperature, because the radial growth rate factor contributes to irregular nanowire shape formation at low temperatures, but the nucleation rate also contributes to irregular nanowire shape formation high temperatures. Since the radial growth rate is slow at high growth temperatures, then at these temperature conditions, the growth time can be increased long enough (8hrs), so that sufficient length (1000nm) can be obtained with well-formed nanowires. If the growth time is increased furthermore (12 hrs), the nanowires will start to merge together into non-hexagonal shapes.
Degree
M.S.M.S.E.
Advisors
Manfra, Purdue University.
Subject Area
Materials science
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