Dislocation behavior in AlN and GaN films grown on vicinal sapphire (0001) substrates were investigated using transmission electron microscopy. It was found that the dislocation behaviors strongly depend on the vicinal angle of the substrates. When the vicinal angle was 0.5°, the dislocation lines propagate along the c-axis and no bending of the dislocation line was found. On the other hand, dislocation bending occurs in the films grown on the 2.0°-off substrates, which resulted in the great reduction of the dislocation density in the films. The dislocation loop formation and the combination of two dislocations into one were the main mechanisms for this reduction. The surface morphology (mono-layer and multilayer step formations) plays an important role in determining the different dislocation behaviors.

Dislocation Behaviour in III-Nitride Epitaxial Films Grown on Vicinal Sapphire (0001) Substrates. X.Q.Shen, H.Matsuhata, H.Okumura: Physica Status Solidi C, 2006, 3[6], 1566-9