Extensive high-resolution electron microscopic investigations were made of known defects such as threading dislocations, inversion domain boundaries and stacking faults. The threading dislocations had their lines oriented mainly parallel to the growth axis, and more than 90% were of α-type. It was possible to analyse their atomic structure by observing them along the [00•1] zone axis. It was found that, when their density was below 1010/cm2, the threading dislocations had 2 atomic configurations: with 8 atom cycles or 5/7 rings along their lines. In highly defective layers, large-angle boundaries were observed and an additional 4-atom ring core was found. When inversion domains were present, they were bounded by {10•0} facets and their boundaries either exhibited Ga-Ga and N-N bonds, or were reconstructed. The 2 atomic configurations were related by a c/2 translation. Although {10•0} non-inversion boundaries had been found in GaN layers, the only non-inversion boundaries found here lay on {11•0} lattice planes. Further investigations showed that they were prismatic faults, and 2 atomic configurations were observed. These had ½<10•1> and 1/6<20•3> displacement vectors. The {11•0} stacking faults were found to fold easily from the prismatic to the basal planes and to originate from a surface step, in the case of growth on (00•1)SiC. The formation of inversion domains was shown to minimize misfit, along the c-axis, in the case of a nanometric step network at the (00•1) sapphire surface.

The Multiple Atomic Configuration and Formation Mechanisms of Extended Defects in Wurtzite GaN. P.Ruterana, J.Chen, V.Potin, G.Nouet: Journal of Physics - Condensed Matter, 2000, 12[49], 10185-94