Epitaxial substrate and method of making the same

An epitaxial substrate and a method to make said epitaxial substrate are disclosed. The epitaxial substrate includes a substrate, a sedimentary layer directly provided on the substrate, a buffer layer provided on the sedimentary layer, and an epitaxial layer provided on the buffer layer. Doping concentration gradually changes in the sedimentary layer, which has a first surface and a second surface opposite to the first surface, wherein a minimum value of the doping concentration is on the first surface. The epitaxial layer is mainly composed of III-V nitride. The substrate and the sedimentary layer are made of a homogeneous material. Whereby, the epitaxial substrate can provide a good heat dissipation performance with low current leakage.