Gallium nitride is one of the III-V semiconductors the most promising in many application areas. Indeed, because of its large direct bandgap (3,4 eV), it can be dedicated to both optoelectronic applications as transistors achieve hyper frequency. It allows the manufacture of components stable at high temperatures and high frequencies. In this work we are interested in the nitriding of gallium arsenide substrates of n-type in order to obtain a thin layer of GaN. The samples were chemically cleaned immediately introduced into the chamber ultra-high vacuum. They then undergo ionic cleaning in situ by argon ions. Spectrometric analyzes do show the absence of any impurities from the surface, in fact, it only detects the presence of gallium and arsenic. Before proceeding to the nitriding of our structures, deposition of gallium is conducted for 20 minutes to send then simultaneously nitrogen and gallium. Analyzes were performed elaborate structures using X-ray photoelectron spectroscopy (XPS). Deposition of mercury (Hg) has been developed on the structures, we have then made an electrical characterization I-V to see the effect of nitriding on the resulting structure.