The present disclosure is directed to an integrated circuit and its formation. In some embodiments, the integrated circuit includes a diffusion barrier layer. The diffusion barrier layer can be arranged to prevent diffusion of the Si and O2 from a Si substrate into a Group III nitride layer. The diffusion barrier layer can comprise Al2O3. In some embodiments, the integrated circuit further comprises a lattice-matching structure disposed between the silicon substrate and a Group III nitride layer.