Growth via low pressure metalorganic vapor phase epitaxy and surface characterization of gallium nitride and indium gallium nitride thin films

The purpose of the research presented herein has been to determine the underlying mechanisms of and to optimize the growth parameters for the growth of smooth surfaces on InGaN and GaN thin films via metalorganic vapor phase epitaxy. Relationships among dislocation density, film thickness, flow rates of the reactants, kinetic growth regime, and thermodynamic growth mode with the surface morphology and surface roughness 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 optimum temperature of 1020°C was found for the former process, below which the islands formed in the growth on AlN buffer layers did not coalesce properly, and above which a hillock growth instability was pervasive on the surface. Increasing the GaN film deposition temperature to 1100°C for GaN film deposition via PE enhanced sidewall growth, however, surface roughness was increased on the (0001) growth plane through the formation of hillocks. Template thickness above 2.5μm had the lowest root mean square surface roughness of 0.48nm over 100μm2. This was attributed to reductions in dislocation density, as measured by corresponding 50% reductions in symmetric and asymmetric full width half maximum values of X-ray rocking curves.; GaN films were grown at 780°C to remove the influence of indium incorporation on the surface roughness. V-defects covered the surface at a density of 2 × 109cm−2 and were linked with a boundary dragging effect. Growth parameters that affect In incorporation into the InGaN film were investigated and measured using room temperature photoluminescence, x-ray diffraction, and x-ray photoelectron spectroscopy. Temperature and growth rate had the greatest effect on incorporation over the range of 760 to 820°C and 25 and 180nm/hr, respectively, through kinetically limiting InN decomposition. Additions of In into the GaN film produced hillock islands that were attributed 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.