This work reports on the latest results of etching of different AlxGa1−x
N/GaN heterostructures in relation to percentage composition of aluminum. The etching processes were carried out in a reactive ion etching (RIE) system using the mixture of BCl3/Cl2/Ar. The topography of the heterostructures surfaces and the slope were controlled using atomic force microsopy (AFM) technique. The photoluminescence spectra were used to determine the surface damage and to calculate the Al content in AlGaN/GaN heterostructures commonly used for high electron mobility transistors (HEMTs) fabrication.