Evaluations of As-fabricated GaN-based light-emitting diodes

We have assessed the structural perfection of as-fabricated light emitting devices using cross-sectional transmission electron microscopy and high resolution transmission electron microscopy. We have used the electron beam induced current and cathodoluminescence techniques to evaluate the electrical activity of the structural defects. Results indicate that the density of threading dislocations in the device structure is about 10 10 cm -2 , and they are of edge character. We argue that this high density is a consequence of the coalescence of the AlN islands that form on the SiC substrates. We also discuss the replication behavior of the threading dislocations during subsequency growth. Both the electron beam induced current and cathodoluminescence images show non-radiative recombination regions. We attribute them to the presence of the threading dislocations.