Article PreviewArticle PreviewArticle PreviewThis paper reports on a structural and electrical analysis of nickel oxide (NiO) films grown both on AlGaN/GaN heterostructures and on 4H-SiC epilayers. The films were grown by metal organic chemical vapor deposition (MOCVD). The structural analysis showed epitaxially oriented films over the hexagonal substrates. The electrical characterization of simple devices onto AlGaN/GaN heterostructures enabled to demonstrate a dielectric constant of 11.7 and a reduction of the leakage current in insulated gate structures. On the other hand, epitaxial NiO films grown onto 4H-SiC epilayers exhibited the presence of an interfacial SiO 2 layer and twinned NiO grains, and a lower dielectric constant.