The present disclosure provides methods for treating a part made from a decomposable semiconductor material, and particularly, methods for detaching a surface film from the rest of such part. According to the provided methods, a burst or pulse of light particles of short duration and very high intensity is applied to the part in order to selectively heat, under substantially adiabatic conditions, an area of the part located at a predefined depth from the surface to a temperature higher than the decomposition temperature of the material, and subsequently a surface film is detached from the rest of the part at the heated area. In preferred embodiments, the decomposable semiconductor material comprises Ga, or comprises AlxGayIn1-x-yN, where 0≦x≦1, 0≦y≦1 and x+y≦1.