GaN device and preparation method thereof

The embodiment of the invention discloses a GaN device and a preparation method thereof. The GaN device comprises a substrate, a buffer layer, an epitaxial layer and a metal electrode layer, wherein the buffer layer, the epitaxial layer and the metal electrode layer are stacked on the substrate in sequence; the epitaxial layer comprises a GaN channel layer, an AlN layer and a barrier layer which are stacked on the substrate in sequence; the metal electrode layer comprises a source-drain metal layer; the source-drain metal layer comprises a protruding structure which extends into the epitaxial layer towards one side of the substrate. According to the mechanism that a source electrode and a drain electrode in a metal electrode layer are in contact with an epitaxial layer to form an ohmic contact electrode, and the source electrode metal electrode layer and the drain electrode metal electrode layer are provided with convex structures which face one side of a substrate and extend into the epitaxial layer, so that