Structural Characterization of Highly Conducting AlGaN (x > 50%) for Deep-Ultraviolet Light-Emitting Diode

Off-axis reciprocal-space mapping was performed on aluminum gallium nitride deep-ultraviolet light-emitting diode base layers. The results indicate that aluminum gallium nitride films growing on aluminum nitride-on-sapphire templates initially grow in compression, nearly lattice matched to the relaxed aluminum nitride buffer layer with approximately 0.5% biaxial strain. This compressive strain may be partially relieved over the course of the thick aluminum gallium nitride growth when a high-quality aluminum nitride and superlattice layer is used. Additionally, a growth interruption appears to allow growth of an unstrained aluminum gallium nitride layer without a gradual release of compressive strain. Growth on a bulk aluminum nitride substrate appears to yield an aluminum gallium nitride layer in tension rather than compression.