Photoluminescence from GaN films grown by MBE on an substrate

GaN films were grown by the MBE method on substrates. Photoluminescence (PL) of the epitaxial films has been studied to characterize the films ex situ. The room-temperature PL spectrum contains an edge PL band and also a broad band of deep-level emission at 2.6 eV. This deep-level emission becomes very small in comparison with the edge emission at helium temperatures. Analysis of the low-temperature data suggests 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 neutral 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 electron - neutral acceptor transition (3.185 eV) in c-GaN. The involved acceptor has a binding energy of about 115 meV.