In this work we report optical experiments on pseudomorphic cubic In xGa1-xN epilayers grown on cubic GaN/3C-SiC templates. We make a detailed study of photoluminescence (PL) and photoluminescence excitation spectroscopy on these samples, with spectra taken at various temperatures (between 2 K and 300 K) and using variable wavelength sources to excite the PL spectra. The combined use of these techniques suggests the existence of indium-rich clusters, constituting a negligibly small fraction of the volume of the total layer. Our results reinforce the notion that the large Stokes-like shift (a difference of approximately 300 meV between emission and absorption) observed in these samples is due to the fact that light absorption occurs in the bulk alloy of average composition while recombination occurs within the indium-rich clusters. © 2006 IOP Publishing Ltd.