Photoluminescence study of excitons in homoepitaxial GaN

High-resolution photoluminescence spectra have been measured in high-qualit y homoepitaxial GaN grown on a free-standing GaN substrate with lower resid ual strain than in previous work. Unusually strong and well-resolved excito nic lines were observed. Based on free- and bound exciton transitions some important GaN parameters are derived. The Arrhenius plot of the free A exci ton recombination yields a binding energy of 24.7 meV. Based on this datum, an accurate value for the band-gap energy, E-G(4.3 K) = 3.506 eV, can be g iven. From the donor bound excitons and their "two-electron" satellites, th e exciton localization energy and donor ionization energy are deduced. Fina lly, estimates of the electron and hole masses have been obtained within th e effective mass approximation. (C) 2001 American Institute of Physics.