We have investigated the energy dependence and depth distribution of the damage caused by ion beam etching using Ar/O2−ions with energies in the range between 175 and 1200 eV. The damage was created by partially etching the upper InP barrier of In0.53Ga0.47As single quantum wells. The optical emission from the quantum wells is used as a high‐resolution local probe for the damage. From the decay of the quantum efficiency as a function of the etch depth we determine an effective damage range of about 8.4 nm for 250 eV ions in InP.