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Homoepitaxy of 3-Nitride Semiconductors

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[Technical Report, Memorandum Report]

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This program focused on understanding the fundamental issues involved in homoepitaxial growth of III-nitride semiconductors with the goal of enabling applications in the fields of high power and rf electronics. The program showed the importance of incoming characteristics of the GaN wafers with roughness, structural defects, degree of offcut, and inhomogeneity impacting homoepitaxial growth and electrical performance in p-i-n and Schottky diodes. Additionally, the utility of long-range characterization of incoming substrates and epitaxy was highlighted and used to first set metrics and then predict electrical performance. The regrowth interface was shown to be compositionally clean in MOCVD growth, except for high levels of Si at the interface. However, this Si did not impact thermal conductivity of the boundary or epitaxial layers at room temperature. Impurities in the nitrides were described in a tutorial on GaN and the optical changes in highly C-doped GaN were explained. Further theoretical work on ultra-wide bandgap nitrides found that holes in AlN will be easily localized reducing the potential for p-type conductivity. Investigations in c-BN found two potential n-type dopants. MAC etching showed a dependence of etch rate on the conductivity and type of material substrate vs. epitaxial layers, but still shows potential in producing deep etching without causing non-radiative defects, which are observed with more conventional plasma-based processes. Finally, in examining MBE-grown RTDs, high performing devices were produced on homoepitaxial structures using optimized surface cleaning and a 2-step growth process. In general, the work in this program sets a foundational base for forming vertical device technologies in our current GaN efforts as well as exploring aspects for ultra-wide bandgap nitride semiconductors.

Subject Categories:

  • Electrical and Electronic Equipment
  • Electricity and Magnetism

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[A, Approved For Public Release]