Threading dislocations in epitaxial InN thin films grown on (0001) sapphire with a GaN buffer layer

Abstract

The density and types of threading dislocations (TDs) in InN thin films grown on (0001) sapphire with a GaN buffer layer were characterized by transmission electron microscopy. Perfect edge TDs with 13〈112̄0〉 Burgers vectors are predominant defects which penetrate the GaN and InN layers. Pure screw and mixed TDs were also observed. Overall the TD density decreases during film growth due to annihilation and fusion. The TD density in GaN is as high as ≈1.5×1011 cm−2, and it drops rapidly to ≈2.2×1010 cm−2 in InN films. Most half-loops in GaN are connected with misfit dislocation segments at the InN/GaN interface and formed loops, while some TD segments threaded the interface. Half-loops were also generated during the initial stages of InN growth.