Low energy Cl species generated in an inductively coupled plasma source have been used to passivate etch induced damage in GaAs and InGaAs. Improved electrical and optical characteristics were measured after Cl2 plasma passivation. The ideality factor and barrier height of etched GaAs Schottky diodes were improved back to the values of an unetched sample with a 10 min passivation. No etching occurred during passivation due to the presence of a surface oxide layer. The growth conditions of the oxide layer were found to have a large effect on the ability of the Cl2 plasma to passivate the surface. It was found that native oxides allow more effective passivation by Cl species as compared to plasma grown oxides. The passivation techniques were used to passivate damage along an etched sidewall for improved electrical conductivity of GaAs wires and increased photoluminescence signal from etched gratings containing an InGaAs quantum well. © 1999 American Vacuum Society.