The defect structures in semi-polar (11•2)-GaN, AlN layers grown on m-sapphire by metal organic vapour phase epitaxy and molecular beam epitaxy were characterized by transmission electron microscopy. The epitaxial relationships were identified as [10•0]GaN||[11•0]sap and [1¯2•3]GaN||[00•1]sap. Defects were identified as mostly partial dislocations, I1-basal and prismatic stacking faults. The density of dislocations was of the order of 5.5 x 109/cm2. They were Frank–Shockley partial dislocations with b = 1/6<20•3> (90%), Shockley partial dislocations with b = 1/3<10•0> (8%) and perfect dislocations of a-type with b = 1/3<11•0> (2%). This was in contrast with the growth in c- or a-orientations, where the large majority of extended defects consisted of perfect dislocations. Upon molecular beam epitaxial re-growth of GaN on metal organic vapour phase epitaxial GaN, no additional defects were generated, although the defects in the substrate propagate through the overgrown layer. However, in the case of molecular beam epitaxial deposition of AlN on metal organic vapour phase epitaxial GaN, new threading dislocations of the type b = 1/3<11•3> were generated taking stepped and curved structures along their lines.

Defect Structure in Heteroepitaxial Semipolar (11-22) (Ga,Al)N. Y.A.R.Dasilva, M.P.Chauvat, P.Ruterana, L.Lahourcade, E.Monroy, G.Nataf: Journal of Physics - Condensed Matter, 2010, 22[35], 355802