Inclined Partial Dislocations in Nitride Semiconductors

초록

We investigate a-type threading edge dislocations (TEDs) and (a+c)-type threading mixed dislocations (TMDs) in (0001) gallium nitride grown on (111) silicon, using the short depth-of-field of a scanning transmission electron microscope equipped with an aberration corrector. Almost all are inclined to the growth direction. While TMDs are known to dissociate into two partial dislocations bounding a prismatic stacking fault, we also observe a similar dissociation of TEDs. Both types of dislocation have straight c-axis segments separated by jogs that displace the dislocation core along an a-axis direction. Jogs on TEDs appear abrupt, with a localized displacement of the whole core by a translation in the basal plane. Conversely, jogs on TMDs are distributed along the dislocation core, giving a variety of structures where individual atom columns are displaced by ±(1/6)[01–10] from one region to the next. Tetrahedral Ga–N bonding, which is preserved in straight TMDs with Drum stacking fault reconstructions, is not maintained in jogs on either type of threading dislocation. We thus expect them to be electro-optically active centers that may have deleterious effects on nitride devices.

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