Etch rates of chemical dry etching (CDE) of GaAs(100) were determined experimentally in the range from 220 to 475 K and dichlorine pressures up to 0.64×10-3 mbar. Model-based understanding of the CDE process is proposed to close the gap between experimental data derived from different setups. With the aid of pseudospecies and carefully selected simplifications all experimental features can be quantitatively explained. The thermal desorption kinetics of dichlorine from the GaAs(100) surface was derived successfully from etch rate data. This model paves the road for an extension to include the ion beam impact influence found in chemically assisted ion beam etching. © 2004 American Vacuum Society.