The cap layers of InAsP/InP SMQWs and InAsP/InGaAsP strained single quantum wells (SSQW) are etched to different depths using ICP. The PL intensity of the quantum wells is enhanced by different degrees after dry etching. The quantum well surface becomes rough and the microstructure inside the quantum well is changed during dry etching. The influence of surface roughness to the photoluminescence of quantum well is eliminated by selectively wet etching the InP cap layer of the SSQW. It is attained that after the cap layer is dry etched off about 20 nm the PL intensity of SSQW is enhanced about 1.8 and 1.2 times due to the change in microstructure and the roughening of surface, respectively.