And etching in chlorine plasmas at 0.3 Torr follows an Arrhenius dependence on substrate temperature. Apparent activation energies, , of and , respectively, were determined from both optical emission of product species, and step height or weight change measurements. For , equals the heat of vaporization of , and the absolute etch rate (7 μm/min at 250°C) is in reasonable agreement with the predicted vaporization rate of . Hence, volatilization of is most likely the rate‐controlling step for etching . Sputter Auger analysis shows that etching in a chlorine plasma leaves multiple layer coverage of on (removable by washing with deionized water), and submonolayer levels of chlorine on . Both surfaces are rich in the group III element. The etched surface morphologies of and are strongly dependent on temperature, exhibiting a rough‐to‐smooth texture transition above ∼250° and ∼120°C, respectively.