High concentrations of Cr (3-5 at. %) were incorporated into GaN during molecular beam epitaxy. There was no evidence of significant formation of deep midgap states due to substitutional Cr acceptors. The results of optical absorption measurements and microcathodoluminescence measurements point to formation of a proper solid solution with the band gap lower than undoped GaN. GaCrN shows n-type conductivity. Increasing the Cr concentration increases the electrical resistivity, leads to a stronger optical absorption in the above-band-gap region, enhances the intensity of the yellow band near 2.3 eV, and promotes the formation of electron traps with the activation energy of 0.2 eV. (C) 2005 American Vacuum Society.