The effects of etch induced damage on the electrical and optical properties of AlGaAs/InGaAs quantum wells (QWs) were studied. From the variations in the photoluminescence (PL) intensity and the conductivity of etched gratings, the optical cutoff width was found to be 33 nm whereas the electrical cutoff width was 136 nm. The PL intensity of the gratings indicated that increased stage power during etching causes more damage. Comparisons were also made between the sheet resistivity (rho(s)) of transmission lines and the conductivity of wires after etching of AlGaAs/InGaAs and AlInAs/InGaAs QWs grown on GaAs and InP substrates, respectively. The AlGaAs/InGaAs QW transmission lines showed reduced rho(s) after etching with higher stage power, although the rho(s) was still higher than that of the unetched control sample. The AlInAs/InGaAs QW transmission lines had a higher rho(s) as the stage power was increased. The two material systems also showed different etch time and sidewall damage characteristics. The AlInAs/InGaAs QW structure degraded more severely at a shorter etch time and had a larger cutoff width as extracted from etched conducting wires.