Optical Characterization of Cubic AlGaN Epilayers by Cathodoluminescence and Spectroscopic Ellipsometry

Cubic AlGaN epilayers grown by molecular beam epitaxy were characterized by cathodoluminescence and spectroscopic ellipsometry techniques. The linear increase of the bandgap energy versus Al composition was consistently confirmed by the two techniques, which indicate the direct transition nature of cubic AlGaN band structure. The energy dependence of optical constants for cubic GaN was also obtained by the simulation of the measured allipsometric data.