Morphology of threading dislocations in high-resistivity GaN films observed by transmission electron microscopy

Morphology of threading dislocations (TDs) in GaN films with different resistivities grown on sapphire by means of metal organic chemical vapor deposition has been investigated using transmission electron microscopy (TEM). GaN films with different resistivities are achieved at various annealing pressures of the nucleation layer (NL). It is observed that the TDs are almost all straight and perpendicular to the sapphire surface in high-resistivity GaN films, while they are significantly bent and interactive in low-resistivity GaN films. The analysis results based on the x-ray diffractometry and TEM demonstrate that the density and morphology of TDs change with annealing pressure of the NL. It is concluded that the annealing pressure of the NL effectively controls the size, density, and coalescence rate of the islands, and thus determines the density and morphology of TDs in GaN. (c) 2007 American Institute of Physics.