High-density plasma etching of GaAs, GaSb, and AlGaAs was performed in ICl/Ar and IBr/AI chemistries using an Inductively Coupled Plasma (ICP) source. GaSb and AlGaAs showed maxima in their etch rates for both plama chemistries as a function of interhalogen percentage, while GaAs showed increased etch rates with plasma composition in both chemistries. Etch rates of all materials increased substantially with increasing rf chuck power, but rapidly decreased with chamber pressure. Selectivities > 10 for GaAs and GaSb over AlGaAs were obtained in both chemistries. The etched surfaces of GaAs showed smooth morphology which were somewhat better with ICl/Ar than with IBr/Ar discharge. Auger Electron Spectroscopy analysis revealed equirate of removal of group III and V components or the corresponding etch products, maintaining the stoichiometry of the etched surface.