Homoepitaxial layers of gallium nitride grown by metalorganic vapour phase epitaxy

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