We have investigated the reactive ion etching of GaInP, GaAs, and AlGaAs. High etching selectivity of GaAs to AlGaAs (or to GaInP) can be achieved due to the formation of aluminum fluoride (AlF3) and indium fluoride (InF3) using a BCl3/SF6 mixture. By using a CH4/H-2 mixture, a polymer film is accumulated on the GaAs surface after reactive ion etching. This polymer film inhibits the reactive ion etching of GaAs. There is no polymer film accumulated on the surface of GaInP. The polymer deposited on the surface of GaInP is removed as the etching products are being removed. Hence, a high etching selectivity of GaInP to GaAs can be achieved by using a CH4/H-2 mixture.