We have grown ZnSe on GaN (0 0 0 1) substrate by MBE. Although the X-ray rocking curve shows that the growth axis of ZnSe is < 1 1 1 >, the samples show only ZnSe-LO Raman signal in the optical arrangement of back-scattering geometry. The photoluminescence (PL) profiles indicate a strong self-activated emission band around 2.1-2.2 eV due to the Zn vacancies. Some structures observed in the PL spectra are due to the resonant Raman scattering corresponding to the LO phonon replica. The PL peaks at 2.85, 2.82 and 2.79 eV are considered to be the Raman signals of 7-, 8- and 9-LO, respectively, from the laser diode 3.06 eV (405 nm) used as the excitation source. (C) 2008 Elsevier B.V. All rights reserved.