The preparation of porous structure on the molecular beam epitaxy (MBE)-grown mixed-polarity GaN epilayers was reported by using the wet chemical etching method.The effect of this porous structure on the residual stress of subsequent-growth GaN epilayers was studied by Raman and photoluminescence (PL) spectrum. Substantial decrease in the biaxial stresse can be achieved by employing the porous buffers in the hydride vapour phase epitaxy (HVPE) epilayer growth. The preparation of porous structure on the molecular beam epitaxy (MBE) -grown mixed-polarity GaN epilayers was reported by using the wet chemical etching method. The effect of this porous structure on the residual stress of subsequent-growth GaN epilayers was studied by Raman Substantial decrease in the biaxial stresse can be achieved by employing the porous buffers in the hydride vapor phase epitaxy (HVPE) epilayer growth.