Inductively coupled plasma (ICP) etching characteristics of GaSb and AlGaAsSb have been investigated in BCl3/Ar and Cl-2/Ar plasmas. The etch rates and selectivity between GaSb and AlGaAsSb are reported as functions of plasma chemistry, ICP power, rf self-bias, and chamber pressure. It is found that physical sputtering desorption of the etch products plays a dominant role in BCl3/Ar ICP etching, while in Cl-2/Ar plasma, the chemical reaction dominates the etching. GaSb etch rates exceeding 2 mu m/min are achieved in Cl-2/Ar plasmas with smooth surfaces and anisotropic profiles. In BCl3/Ar plasmas, etch rates of 5100 and 4200 Angstrom/min are obtained for GaSb and AlGaAsSb, respectively. The surfaces of both GaSb and AlGaAsSb etched in BCl3/Ar plasmas remain smooth and stoichiometric over the entire range of plasma conditions investigated. This result is attributed to effective removal of etch products by physical sputtering. For a wide range of plasma conditions, the selectivity between GaSb and AlGaAsSb is close to unity, which is desirable for fabricating etched mirrors and gratings for Sb-based midinfrared laser diodes.