The structural and optical characteristics of porous GaN prepared by Pt-assisted electroless etching under different etching durations are reported. The porous GaN samples were investigated by scanning electron microscopy (SEM), high-resolution X-ray diffraction (HR-XRD), photoluminescence (PL) and Raman scattering. SEM images indicated that the density of the pores increased with the etching duration; however, the etching duration has no significant effect on the size and shape of the pores. XRD measurements showed that the (0 0 0 2) diffraction plane peak width of porous samples was slightly broader than the as-grown sample, and it increased with the etching duration. PL measurements revealed that the near band edge peak of all the porous samples were red-shifted; however, the porosity-induced PL intensity enhancement was only observed in the porous samples; apart from that, two additional strain-induced structural defect-related PL peaks observed in as-grown sample were absent in porous samples. Raman spectra showed that the shift of E-2 (high) to lower frequency was only found in samples with high density of pores. On the contrary, the absence of two forbidden TO modes in the as-grown sample was observed in some of porous samples. (c) 2007 Elsevier B.V. All rights reserved.