Optical properties of GaN epitaxial layers grown by low-pressure metalorganic vapor phase epitaxy under various growth conditions

Optical Properties have been studied on hexagonal GaN epilayers grown on the sapphire substrate by low-pressure metalorgnic vapor phase epitiaxy under systematically changing growth parameters as growth temperature (T-g: 900-1110 degreesC) and pressure (P-g:40-500 Torr). Photoluminescence (PL) lines related to excitons, donor-acceptor pair PL, BL band (2.8 eV) and YL band (2.3 eV) have been studied with relation to growth parameters. At low P-g of 80 Torr, crystal quality of epilayers in view of PL properties tends to be the best at 1000 degreesC. At high P-g (300 and 500 Torr), crystal quality increases monotonically with T-g up to 1050 degreesC. Similar result has been obtained for the broadening of photoreflectance (PR) spectra. In this study, the best quality epilayer was grown at T-g = 1050 degreesC and P-g = 500 Torr, which are the highest T-g and P-g.