Effects of ion‐beam and chemical etching on the optical properties of GaAs were studied by means of cathodoluminescence. An important degradation of the radiative properties is observed at the surface as well as in depth. This degradation is not removed by the ohmic contact annealing process at 450 °C. In the case of chemical etching, a complex behavior of the luminescence properties after annealing is indicative of surface‐states modifications. To optimize the etching procedure, we defined a process combining an ion‐beam etching at 250 eV and a short‐duration chemical etching.