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Keywords:

  • electron microscopy;
  • InN;
  • interfaces;
  • semipolar

Abstract

Based on bicrystal symmetry and transmission electron microscopy observations, we elaborate on the coexistence of the two orientation variants of semipolar s-plane (equation image) InN epilayers grown on r-plane sapphire by plasma-assisted molecular beam epitaxy (PAMBE). It is shown that variant coexistence is favored by a high order of coincident symmetry ensuring significant lattice continuity. The (0002) || (equation image) low-energy grain boundary was identified to principally delimit the two InN variants. Aside of the variant coexistence, the InN/sapphire interface was observed to comprise protrusions attributed to the InN buffer layer growth. Rapid thermal annealing was employed in order to improve the epilayer quality and it was found to induce defect reduction attributed to dislocation glide. However, the InN/sapphire interface was adversely affected by this process.