Partial Edge Dislocations Comprised of Metallic Ga Bonds in Heteroepitaxial GaN.

We investigated the atomic structure of inclined threading edge dislocation (TED) typically observed in GaN grown on Si(111) through (scanning) transmission electron microscopy. Atomic observations verified that the inclined TED consisted of two partial dislocations. These results imply that the inclined TED possesses a Ga-Ga atomic configuration that is energetically unfavorable. However, the introduction of such structures is considered unavoidable because the TEDs should climb regularly to mediate the applied stress or the increasing surface due to the buffer layer. This Ga-Ga configuration is highly likely to form metallic bonds and appears to be the primary reason for the inferior efficacy of a GaN light-emitting diode grown on Si(111).