The melt growth of bulk GaN crystals is hindered by high nitrogen pressure (∼45000 atm) at melting point. Recently, bulk GaN crystals were grown at a pressure of ∼100 atm by means of Na flux. However, the flux growth method failed to control the nucleation site and growth orientation of GaN. In this work, oriented GaN crystals were obtained by means of a seeded Na flux method with the addition of oriented AlN(0001) film to the growth ambient. The nucleation of bulk GaN was spatially confined to the top surface of the AlN film and grown with the GaN[0001] axis parallel to the AlN[0001] axis. In contrast, no bulk GaN was observed on the SiC(0001) surface which was also lattice matched with the GaN. Both X-ray diffraction (XRD) and cathodoluminescence confirm the high quality of the as-grown GaN.
The 2075°C melting temperature of boron has hindered the growth of hexagonal boron nitride (h-BN) crystal. The use of Si flux was reported to decrease the growth temperature to 1850°C. In this work, we discovered Na as a new flux for the growth of h-BN crystals at a temperature as low as 700°C. The growth of h-BN detected by X-ray diffraction (XRD) was consistent with the hexagonal features observed by scanning electron microscopy (SEM). Absorption at ∼1372 cm-1 was indicated by Fourier transform infrared (FTIR) spectroscopy. This absorption was attributed to the in-plane B-N stretching mode of h-BN. Emissions at photon energies as high as ∼5.6 eV are observed from cathodoluminescence (CL) spectra, indicating an optical band gap of at least 5.6 eV.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.