We use photoreflectance (PR) spectroscopy to study the electronic band structure modification of GaN films grown along different nonpolar orientations due to biaxial, anisotropic in-plane strain. The exciton transition energies of an unstrained, high-quality C-plane GaN film are used to accurately determine the crystal-field and spin-orbit splitting energies. For films with a nonpolar orientation, the resonant features observed in the PR spectra exhibit a strong in-plane polarization anisotropy and different transition energies from the ones measured in the C-plane GaN film. The deformation potential D-5 is accurately determined from four GaN films with a nonpolar orientation using the measured energies together with the polarization properties and out-of-plane strain. (c) 2006 American Institute of Physics.

M-plane In0.1Ga0.9N(1 (1) over bar 00) multiple quantum wells were grown on gamma-LiAlO2(100) by plasma-assisted molecular-beam epitaxy. The high brightness of the photoluminescence of these multiple quantum wells and the observation of band-edge emission from the barriers are consistent with the expected absence of spontaneous and piezoelectric polarization fields along the growth direction. Despite this fact, the recombination dynamics observed is rather complex and is shown to originate from the superposition of exciton relaxation towards a band of localized states and simultaneous recombination.