High-resolution transmission electron microscopy (HRTEM) observation of dislocation structures in AlN thin films

The structure and configuration of threading dislocations (TDs) in AlN films grown on (0001) sapphire by metal-organic vapor phase epitaxy (MOVPE) were characterized by high-resolution transmission electron microscopy (HRTEM). It was found that the TDs formed in the films were mainly the perfect edge dislocations with the Burgers vector of b = 1/3 < 11 (2) over bar0 >. The majority of the edge TDs were not randomly formed but densely arranged in lines. The arrays of the edge TDs were mainly observed on the {11 (2) over bar0} and {10 (1) over bar0} planes. These two planes showed different configurations of TDs. TD arrays on both of these planes constituted low-angle boundaries. We suggest that these TDs are introduced to compensate for slight misorientations between the subgrains during the film growth.