Avoiding defects

Recent work from North Carolina State University describes a technique for reducing defects in gallium nitride (GaN) epitaxial films grown on sapphire substrates (‘Embedded voids approach for low defect density in epitaxial GaN films’, Appl. Phys. Lett. 98, 023115 (2011), 17 January and this link). By embedding a series of high density micro-voids within thin films, the group were able to create sinks or termination sites for dislocations. According to the team, TEM and AFM analysis confirm dislocation density reductions of 2-3 orders of magnitude with particular benefits for LEDs emitting in the ultraviolet range.