BCl3reactive ion etching for gate recessing of GaInP/InGaAs/GaAs pseudomorphic high electron mobility transistors (PHEMTs) is found improved by the addition of an appropriate amount of Ar to the gas flow. The influence of theBCl3/Argas flow ratio on GaAs to GaInP etch selectivity, surface roughness, and surface damage was studied. The results indicate that the conditions for minimum plasma damage, as determined by photoreflectance (PR) spectroscopy, corresponded with the conditions for minimum surface roughness, as determined by atomic force microscopy (AFM). The optimalBCl3/Argas flow ratio for minimum surface damage and roughness was found to be 6:4. TwoBCl3:Arflow rate ratios, 6:4 (optimal ratio) and 10:0 (pureBCl3)were used for gate recess etching in the fabrication of GaInP/InGaAs/GaAs PHEMTs. From drain–source current to gate–source voltage(Ids–Vgs)measurements, it was found that the plasma-induced damage for the sampleScdry etched with 6:4BCl3/Aris less than that of the sampleSedry etched with pureBCl3.The dc and small signal rf characteristics of PHEMTScwere superior to those of the wet-etched PHEMTS0and PHEMTSedry etched with pureBCl3.The improvement is attributed to the lower parasitic source resistance associated with the tighter recess geometry of theBCl3plasma recess device. These results show that photoreflectance spectroscopy is a powerful tool for investigating surface damage and can be used to improve the performance of PHEMTs.