The dry etching characteristics of GaAs, AlGaAs, and GaSb in BCl3/Ar or Cl2/Ar high density discharges were examined over the substrate temperature range -30 to +60-degrees-C. Sidewall etching is suppressed at temperatures of less-than-or-equal-to -20-degrees-C and the vertical etch rates of all three materials decrease by factors of two or more in the range from 0 to -30-degrees-C. Condensation of etchant and product species occurs at -30-degrees-C in both BCl3/Ar and Cl2/Ar discharges, leading to rough surface morphologies. Use of a bottom collimating magnet on the electron cyclotron resonance source produces faster etch rates at room temperature, but has little effect at -30-degrees-C because of the condensation problem.