Growth via Low Pressure Metalorganic Vapor PhaseEpitaxy and Surface Characterization of GaN and In(x)Ga(1-x)N Thin Films.

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Title: Growth via Low Pressure Metalorganic Vapor PhaseEpitaxy and Surface Characterization of GaN and In(x)Ga(1-x)N Thin Films.
Author: Miraglia, Peter Quinn
Advisors: Robert F. Davis, Chair
Robert J. Nemanich, Major
Salah M. Bedair, Major
Mohamad M. Bourham, Minor
Abstract: he purpose of the research presented herein has been to determine the underlyingmechanisms of and to optimize the growth parameters for the growth of smooth surfaceson InGaN and GaN thin films via metalorganic vapor phase epitaxy. Relationshipsamong dislocation density, film thickness, flow rates of the reactants, kinetic growthregime, and thermodynamic growth mode with the surface morphology and surfaceroughness were determined. The two chief parameters affecting template surface roughness in both growth of GaN above 1000°C were determined to be temperature and layer thickness. An optimumtemperature of 1020°C was found for the former process, below which the islands formedin the growth on AlN buffer layers did not coalesce properly, and above which a hillockgrowth instability was pervasive on the surface. Increasing the GaN film depositiontemperature to 1100°C for GaN film deposition via PE enhanced sidewall growth;however, surface roughness was increased on the (0001) growth plane through theformation of hillocks. Template thickness above 2.5 microns had the lowest root mean squaresurface roughness of 0.48nm over 100 square microns. This was attributed to reductions indislocation density, as measured by corresponding 50% reductions in symmetric andasymmetric full width half maximum values of X-ray rocking curves. GaN films were grown at 780°C to remove the influence of indium incorporationon the surface roughness. V-defects covered the surface at a density of 2E9 per square centimeter andwere linked with a boundary dragging effect. Growth parameters that affect Inincorporation into the InGaN films were investigated and measured using roomtemperature photoluminescence, x-ray diffraction, and x-ray photoelectron spectroscopy.Temperature and growth rate had the greatest effect on incorporation over the range of760 to 820°C and 25 and 180nm/hr, respectively, through kinetically limiting InNdecomposition. Additions of In into the GaN film produced hillock islands that wereattributed to a strain relief mechanism. The V-defects were also observed in InGaN films;however, their formation was suppressed below a nominal thickness of 25nm
Date: 2001-07-13
Degree: PhD
Discipline: Materials Science and Engineering

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