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Characterization of Dark-Block Defects in Cantilever Epitaxial GaN on Sapphire

  • P. P. Provencio (a1), D. M. Follstaedt (a1), N. A. Missert (a1), D. D. Koleske (a1), C. C. Mitchell (a1), A. A. Allerman (a1) and C. I. H. Ashby (a1)...


Cantilever epitaxy of GaN on sapphire has been augmented by the use of initial facetted GaN growth on narrow sapphire mesas (< 1μm) in order to turn remaining threading dislocations from vertical to horizontal, and thus reduce the overall dislocation density at the surface where devices would be placed. With this modification, isolated non-radiative block-like defect areas have been introduced that hinder optical and electronic material performance. Here we characterize these defects with microscopy, and show that they are arrays of lateral dislocations, with cracks and voids along their centerlines. We deduce that they result when tilted GaN is joined to neighboring oriented material. Their presence is independent of the type of nucleation layer used.



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