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In this paper, we report the formation of porous GaN films under a novel alternating current (sine-wave a.c. (50 Hz)) photo-assisted electrochemical etching (ACPEC) conditions. The ac formed porous GaN with excellent structural and optical properties. Field emission scanning electron microscope (FESEM) micrographs indicated that the shapes of the pores are high quality hexagonal like and nano-building structures. The porous layer exhibited a substantial photoluminescence (PL) intensity enhancement with red-shifted band-edge PL peaks associated with the relaxation of compressive stress. The shift of E2(high) to the lower frequency in Raman spectra of the porous GaN films further confirms such a stress relaxation