Lateral migration of dislocations in oxygen-doped GaN grown by molecular beam epitaxy

Threading dislocations in gallium nitride epilayers intermittently doped with oxygen were examined using transmission electron microscopy. Dislocations of all types were observed to incline away from the [0001] growth direction at the first introduction of oxygen, remaining inclined through subsequently doped layers. The type and the sign of the Burgers vector of inclined dislocations were characterized by large angle convergent beam electron diffraction, which revealed that the direction of inclination was not primarily driven by misfit stresses. In contrast, dislocations were observed to incline towards pronounced surface pits. It is concluded that the inclination is driven by surface roughening induced by oxygen doping, in contrast to previously published results.