Electron cyclotron resonance (ECR) plasma etching with additional rf-biasing produces etch rates greater than or equal to 2,500 A/min for InGaP and AlInP in CH4/H-2/Ar. These rates are an order of magnitude or much higher than for reactive ion etching conditions (RIE) carried out in the same reactor. N-2 addition to CH4/H-2/Ar can enhance the InGaP etch rates at low flow rates, while at higher concentrations it provides an etch-stop reaction. The InGaP and AlInP etched under ECR conditions have somewhat rougher morphologies and different stoichiometries up to similar to 200 Angstrom from the surface relative to the RIE samples.