PHOTOLUMINESCENCE FROM GAN FILMS GROWN BY MBE ON LIGAO2 SUBSTRATE

GaN films were grown by the MBE method on LiGaO2 substrates. Photolumi nescence (PL) of the epitaxial films has been studied to characterize the films ex situ. The room-temperature PL spectrum contains an edge P L band and also a broad band of deep-level emission at 2.6 eV. This de ep-level emission becomes very small in comparison with the edge emiss ion at helium temperatures. Analysis of the low-temperature data sugge sts that the films contain both hexagonal and cubic crystallites. The main PL lines at 5.7 K are due to emission of excitons bound on neutra l donors in hexagonal and cubic phases of the epitaxial film (3.472 eV and 3.263 eV), D-A pair recombination (3.154 eV) and also free electr on-neutral acceptor transition (3.185 eV) in c-GaN. The involved accep tor has a binding energy of about 115 meV.