Observation of coreless edge and mixed dislocations in Mg-doped Al0.03Ga0.97N

Transmission electron microscopy has been used to examine the core structure of threading dislocations in heavily Mg-doped Al0.03Ga0.97N thin films. It is shown that edge and mixed, but not screw, dislocations have hollow cores with diameters typically 1-5 nm. A model is presented where hollow core formation is initiated by the segregation and subsequent precipitation of Mg at these dislocation cores. The implications for understanding the formation of hollow core dislocations in other GaN films are discussed. (C) 2002 American Institute of Physics.