Growth of GaN on SiC/Si substrates using AlN buffer layer under low III/V source gas ratio by hot-mesh CVD

GaN is a widegap compound semiconductor, which is useful for optoelectronic devices operating in short wavelengths and at high-temperatures. The GaN films are usually grown on sapphire substrates at growth temperatures higher than 1000°C using MOCVD method. For the growth of GaN films with excellent crystallinity and optical property, high V/III source gas ratio (NH₃/TMG>;10,000) is required due to the decomposition-resistant property of nitrogen source-gas such as NH₃. The reduction of the source gas consumption is strongly desired from the viewpoint of the resource savings. For the GaN growth at low V/III source gas ratios, excitation of NH₃ is required. Among several methods, catalytic reaction of hot tungsten (W) wire surface with NH₃ is very promising, because it produces high-density NH_x radicals, in particular when the W fine wires with a mesh structure are used. Recently, heteroepitaxial growth of GaN films on Si substrates has been attempted, aiming at fabrication of various GaN electronic devices at a low cost. A large lattice mismatch, however, also exists between GaN and Si, which is similar to the case between GaN and sapphire. In order to overcome this problem, insertion of a thin SiC buffer layer between them is useful. In our previous studies, GaN films were grown on SiC/Si(111) substrates by hot-mesh CVD using TMG and NH₃. Photoluminescence spectra of GaN films grown on the SiC buffer layer, however, showed relatively strong yellow luminescence at RT. In this study, in order to further improve the crystallinity and the optical property, the insertion of AlN buffer layer between GaN and SiC layer was attempted.