It was found that, in the absence of threading dislocations in InxGa1-xN/GaN heterostructures, coherent generation of misfit dislocations occurred for x>0.11 in 100nm-thick epilayers. In particular, a study was made here of In0.17Ga0.83N grown onto a low defect-density GaN free-standing substrate (with 1.9% lattice mismatch). A diffraction contrast analysis carried out in the transmission electron microscope showed straight line defects with Burgers vectors 2/3<11▪0> (i.e., 2a, where a was the hexagonal plane lattice parameter), which extended many micrometers approximately along <1¯1▪0> directions and with an average lateral spacing of 90nm. Although these defects were complex and mostly sessile, evidence was found that they could dissociate into glissile misfit dislocations with Burgers vectors of 1/3<11▪0>. It was proposed that the defects were generated by a punch-out mechanism involving slip on inclined prismatic planes. The properties of these defects and their role in relieving misfit strains were considered.

Misfit Dislocation Generation in InGaN Epilayers on Free-Standing GaN. R.Liu, J.Mei, S.Srinivasan, H.Omiya, F.A.Ponce, D.Cherns, Y.Narukawa, T.Mukai: Japanese Journal of Applied Physics, 2006, 45[22], L549-51