Homoepitaxial Growth of GaN Layers by Reactive Molecular-Beam Epitaxy on Bulk GaN Single Crystals Prepared by Pressure-Controlled Solution Growth

Abstract

We have performed the homoepitaxial growth of GaN layers by reactive molecular-beam epitaxy (MBE) on both sides (Ga- and N-faces) of the bulk GaN single crystals prepared by the pressure-controlled solution growth (PC-SG) method. High-crystalline-quality GaN layers, which showed a narrow full-width at half maximum (FWHM) for the (002) plane in X-ray rocking curve measurements and no dark spot in the cathodoluminescence images, were obtained both on the Ga- and N-faces. It was indicated that the incorporation mechanism of residual impurities and/or defects is different between the homoepitaxial layers on the Ga- and N-faces, and that a larger amount of residual donors and nonradiative recombination centers existed in the homoepitaxial layer on the N-face. In addition, our results suggest that the poor quality of N-polarity GaN epilayers grown by conventional MBE is caused not only by the high density of nanometric inversion domains (IDs) in the N-polarity matrix, but also by polarity-related effects.