Growth and characterization of metalorganic chemical vapor deposition InGaN

The growth of InGaN with up to 53% InN content by the metalorganic chemical vapor deposition (MOCVD) technique has been conducted. The purpose of this study was to develop an understanding of the complex behavior of In incorporation on growth conditions. MOCVD growth of the nitrides requires higher temperatures than is typically experienced during the deposition of other III-V materials. This requirement was factored into the design and construction of an MOCVD system built specifically for the growth of III-nitrides. High quality heteroepitaxy nitride deposition also requires an adequate nucleation layer to enhance the properties of these wide band gap semiconductors. Two new methods for nucleation layer growth, atomic layer epitaxy (ALE) and molecular stream epitaxy were investigated and proven to adequately enhance GaN deposition. The ALE nucleation layer was utilized for the growth of the MOCVD InGaN films studied in this work.; InN incorporation in InGaN has been observed to increase with decreasing growth temperature, increasing In and/or Ga flux, and first increase and then plateau with increasing V/III ratio. Additionally, metallic In droplets can form on the nitride film surface under non-optimized growth conditions. These results were explained by considering the possible reaction pathways available to the In species: Incorporation, desorption, and In metal formation. A dependence of the In incorporation rate on very low flow rates of hydrogen was discovered and explained by a site blocking effect of the hydrogen at the surface hindering the incorporation of the In. This hydrogen adsorbed on the surface was also responsible for the observed decrease in the hydrogen, carbon, and oxygen impurity concentrations in the film. These InGaN epitaxial films were also analyzed to determine the occurrence of phase separation in the InGaN material system. A transition from single phase to multiphase InGaN was observed to occur between 21 and 28% In content and was shown to agree with the theoretically calculated GaN-InN pseudo-binary phase diagram.