Nickel oxide and cerium oxide thin films have been grown by metal-organic chemical vapor deposition on AlGaN/GaN heterostructures. Thin and epitaxial layers have been already obtained at low temperature (500 °C). Despite the two oxides possess the same crystal structure (face cubic centered compounds), different structural relationships have been observed with respect to the substrate. In particular, nickel oxide films were epitaxially grown along the direction, while cerium oxide thin films showed and preferential orientations. These structural relationships have been justified by geometric and/or kinetics factors. In both cases, the epitaxial growth has been obtained at low temperature by the implementation of two second generation metal precursors, namely the nickel 2-thenoyl-trifluoroacetonate adduct with the tetramethylethylendiamine and cerium 1,1,1,5,5,5-hexafluoroacetlyacetonate …