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Eric's Project Page - RISE summer 2003 |
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Intern: Eric Fraser, Pomona College
Mentor: Ed Letts
Faculty Supervisor: Shuji Nakamura
Department: Materials |
CHARACTERIZATION OF NITRIDE-BASED CRYSTALS FOR OPTICAL DEVICES
Various nitride-based compounds have been grown on sapphire substrates to be
used in solid-state lighting devices. Two of the most popular techniques for
growing the nitrides are Metalorganic Chemical Vapor Deposition (MOCVD) and
Hydride Vapor Phase Epitaxy (HVPE). MOCVD is used in this lab primarily to grow
thin films of varying compositions; HVPE is used primarily to grow bulk GaN.
The resulting samples can be processed to construct lighting devices that yield
significant energy savings, lower heat output, and longer lifetimes compared
to current lighting methods (incandescent, fluorescent, halogen, etc.). These
devices require high-quality crystals. Therefore, the compounds — specifically
GaN, InGaN, and AlN — must be characterized to determine crystal quality and
the growth conditions must be optimized to improve quality. Atomic Force
Microscopy (AFM) and X-Ray Diffraction (XRD) techniques were used to
characterize the samples. Data on crystal quality, crystal orientation,
dislocations, impurities, and composition was gathered using these techniques.
The examined crystals varied widely in quality. Growth conditions, including
growth temperature, pressure, and relative composition of elements, are thus
optimized based on characterization data from previous growths.
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