HOMOEPITAXIAL LAYERS OF GALLIUM NITRIDE GROWN BY METALORGANIC VAPOR-PHASE EPITAXY

Gallium nitride epitaxial layers were grown by metalorganic vapour pha se epitaxy (MOVPE) on bulk GaN crystals. These substrates were grown a t high temperature (about 1800 K) and high pressure (about 15 kbar). M OVPE was carried out in a vertical growth chamber at atmospheric press ure, NH3 was used as the nitrogen precursor. The layers were examined using x-ray diffraction and optical photoluminescence. It was found th at most of the layers exhibit smaller lattice constants than the subst rates, which indicates a smaller concentration of point defects and fr ee electrons. The photoluminescence spectra consist of sharp (down to 1.2 meV) near-band-edge peaks attributed to the excitons bound to neut ral donors and broad yellow peaks centred at 2.3 eV.