Abstract: A GaN-on-Si epiwafer forming a layer stack is described. The epiwafer including a substrate, a strain-decoupling layer including a surface recovery layer and a self-organized template layer arranged directly on the substrate, the self-organized template layer comprising pits, and comprising GaN, the surface recovery layer having a substantially smooth surface, and a strain-engineering sub-stack arranged on the self-organized template layer and comprising at least one GaN layer and at least one AlxGa1?xN intermediate layer.