Hollow core dislocations in Mg-doped AlGaN

Transmission electron microscopy has been used to investigate the core structure of threading dislocations in heavily Mg-doped (10 20 cm −3 ) Al 0.03 Ga 0.97 N films grown on (0001) sapphire by metal-organic chemical vapour deposition. Evidence is presented that Mg segregates to edge and mixed dislocations, and that these dislocations often have open cores with diameters in the range 1–5nm. The mechanism of hollow core formation and the role of Mg are discussed.