The alloy and lattice disorder as well as the annealing behaviour of 0.5 μm thick AlxGa1-xN films on sapphire substrate after implantation of 181Hf(181Ta) was studied using the perturbed angular correlation (PAC) technique. AlxGa1-xN samples with different molar fractions of AlN were implanted with a fluence of 1×1013 at/cm2 of the radioisotope 181Hf with an energy of 160 keV at the Bonn Isotope Separator. Subsequently the samples were annealed in a rapid thermal annealing apparatus at temperatures up to 1100°C in nitrogen atmosphere. The strength of the electric field gradient, which is caused by the wurtzite structure of the host lattice at the probe site, varies linearly with the concentration x of aluminium in the ternary compound. The uniformity of this hyperfine interaction has its minimum at x≈0.6.