It was recalled that SiNx interlayers could act as anti-surfactants and drastically reduce the dislocation density in pure GaN layers. In the present work, very efficient dislocation annihilation of the a-type threading dislocations was observed at a fractional SiNx monolayer; even in AlxGa1−xN layers with the relatively high Al content of x = 0.2, grown onto c-plane sapphire by MOVPE. The investigations were focused on the effect of the SiNx interlayer on the dislocation density reduction of the a-type threading dislocations. Weak-beam dark-field and high-resolution transmission electron microscopic analyses directly at the SiNx interface indicated that the most frequently occurring effect for the reduction of the a-type threading dislocations was the conversion of an a-type threading dislocation into an a-type basal dislocation due to lateral overgrowth of SiNx by AlGaN. To confirm this effect, an appropriate dislocation model was developed for the a-type threading dislocation in AlGaN and its bending due to the SiNx nano-mask. Corresponding image calculations were performed and compared with the experiments.

Simulation Supported Analysis of the Effect of SiNx Interlayers in AlGaN on the Dislocation Density Reduction. O.Klein, J.Biskupek, U.Kaiser, K.Forghani, S.B.Thapa, F.Scholz: Journal of Physics - Conference Series, 2010, 209[1], 012018