Exciton-related photoluminescence in homoepitaxial GaN of Ga and N polarities

A photoluminescence (PL) study of GaN homoepitaxial layers grown by metal-organic chemical-vapor deposition demonstrates the high optical quality of N-face layers deposited on vicinal (000 (1) over bar) GaN substrates. In contrast to broad PL emission in exact (000 (1) over bar) layers, narrow-bound (0.9 meV) and free- (A and B) excitonic transitions are observed. By following the PL spectra as a function of temperature and excitation power, the main optical transitions in the Ga- and the misoriented N-face layers are found to be the same. Observed differences are related to the distinct creation of donor and acceptor states in the samples of different polarities. (C) 2000 American Institute of Physics. [S0003-6951(00)02317-2].