Large exciton g-factors in anisotropically strained A-plane GaN film measured using magneto-optical Kerr effect spectroscopy

Abstract

Exciton Landé g-factors in wurtzite GaN epitaxial films with (0001) C-plane and (11 2 ̄0) A-plane orientations have been measured in magnetic fields B up to 1.8 T, using polar magneto-optical Kerr effect (MOKE) spectroscopy. A procedure is developed for extracting the Zeeman splitting and thereby the g-factor, from Kerr ellipticity and rotation spectra of A-plane films, which have in-plane polarization anisotropy. In the C-plane film the measured g-factors for the A, B, and C exciton transitions were g A = 0.09 ± 0.02, g B = 0.74 ± 0.05, and g C = 3.9 ± 0.2, respectively, with Bc-axis and comparable to earlier reports. The MOKE spectra of the A-plane film have one dominant exciton feature each for analyzer axis and to the c-axis of GaN, and they arise at different energies. The measured g-factors for these were much larger, with values g = 4.7 ± 1 and g | | c = 7.1 ± 1.2 with Bc-axis. Comparison with a k·p perturbation theory based calculation, which included the influence of strain, indicates that the features in the A-plane film are associated with exciton transitions involving bands that are strongly mixed by the anisotropic in-plane strain. © 2013 AIP Publishing LLC.