Tungsten carbide (WC) contacts have been investigated as an original gold-free Schottky metallization for AlGaN/GaN heterostructures. The evolution of the electrical and structural/compositional properties of the WC/AlGaN contact has been monitored as a function of the annealing temperature in the range from 400 to 800 C. The Schottky barrier height (Φ B) at the WC/AlGaN interface, extracted from the forward current-voltage characteristics of the diode, decreased from 0.82–0.85 eV in the as-deposited and 400 C annealed sample, to 0.56 eV after annealing at 800 C. This large reduction of Φ B was accompanied by a corresponding increase of the reverse leakage current. Transmission electron microscopy coupled with electron energy loss spectroscopy analyses revealed the presence of oxygen (O) uniformly distributed in the WC layer, both in the as-deposited and 400 C annealed sample. Conversely, oxygen …