Photoluminescence (PL) was used to study the damage of (100) GaAs surfaces exposed to BCl3/Ar plasma generated by an electron cyclotron resonance system. With PL measurement of strained InGaAs/GaAs quantum wells within the etched top GaAs layer, our analysis shows that this technique assesses damages to the structure not detected by atomic force microscopy and photoreflectance. A transport model is used to show a 100 times reduction in the Debye length for a 100 nm layer underneath the etching surface. (c) 2006 American Vacuum Society.