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Microstructural evolution of a-plane GaN grown on a-plane SiC by metalorganic chemical vapor deposition

  • Author(s): Craven, M D
  • Wu, F
  • Chakraborty, A
  • Imer, B
  • Mishra, U K
  • DenBaars, S P
  • Speck, J S
  • et al.
Abstract

This letter describes the relationship between the morphological evolution of heteroepitaxial a-plane GaN films and the formation of the extended defect structure. The initial a-plane GaN growth on a-plane SiC substrates (via a high temperature AlN buffer layer) follows a Volmer-Weber growth mode. Consequently, the coalescence of three-dimensional (3D) islands generates threading dislocations which dominate the nonpolar GaN film's microstructure (3x10(10) cm(-2)). Exposed nitrogen-face surfaces, identified using x-ray diffraction measurements and convergent beam electron diffraction analysis, are present throughout the 3D growth and are the likely source of basal plane faulting (7x10(5) cm(-1)) within the film. Atomic force microscopy and scanning electron microscopy were used to image the morphological transition, which was correlated to changes in the a-GaN crystal tilt mosaic measured by x-ray rocking curves. (C) 2004 American Institute of Physics.

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