Comparison of HVPE GaN films and substrates grown on sapphire and on MOCVD GaN epi-layer
In this study, we report the results of comparison of GaN film properties grown on bare sapphire and on MOCVD GaN epi-layer. Comparing with properties of two GaN films, we used double crystal X-ray diffraction (DCXRD), scanning electron microscopy and cathodoluminescence (CL) spectroscopy and imaging techniques. As a result of these measurements, we found that GaN films grown on MOCVD GaN epi-layer are of better quality than GaN films grown on sapphire substrate. After removing the sapphire substrates, the quality of GaN substrate grown on MOCVD GaN epi-layer is much better than that of GaN substrate grown on sapphire. As a result, we found that nucleation layer such as MOCVD GaN epi-layer influences the crystal and optical properties of HVPE GaN film.