In order to facilitate resuming molecular beam epitaxy after etching a substrate or an epitaxial layer, the etching method is implemented in an ultra-high vacuum, and it consists in producing at least two simultaneous chemical beams converging towards the substrate or the layer, the beams being formed of substances, each of which is capable of reacting with elements of different types in the substrate or the layer so as to form volatile compounds. Application in particular to manufacturing photonic and optoelectronic components.