Investigation of the growth characteristics of epitaxial GaN layers on sapphire by microcathodoluminescence

A study was made of the growth regimes of undoped epitaxial GaN layers under various substrate nitriding conditions. It was observed that at a nitriding temperature of ∼1000 °C films are formed with typical growth characteristics in the form of hexagonal pyramids separated by a smoothed surface. The cathodoluminescence pattern in the pyramids revealed a fine structure in which a region of donor-acceptor recombination could be identified. The formation of acceptor levels in this region was attributed to intrinsic structural defects in the GaN layers with unsaturated (broken) bonds. The presence of a donor-acceptor recombination line in mirror-smooth epitaxial films may indicate that these films contain this type of structural defect.

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