Movement of a-type dislocations in AlN under electron beam irradiation

Significant a-type dislocation movement was directly observed in AlN films using a transmission electron microscope (TEM). Most of the a-type dislocations are arranged in arrays, which are similar in structure to the low-angle grain boundaries, and are unable to move under electron beam irradiation. Only a small number of bending dislocations, away from those dislocation arrays, could be excited to glide by electron beam irradiation. These moving dislocations can travel a rather long distance along the 〈0001〉 direction until their movements are stopped by the free surface or by the interface of the sample, and in some cases, by dislocation arrays. Finally, this letter presents a comprehensive analysis of electron-irradiation-enhanced dislocation glide in AlN, with the role of the stress state in the dislocation movement under uniaxial stress conditions particularly emphasized. (paper)