Atomic layer deposition of barrier metal layer for electrode of gallium nitride material device

An electrode structure for a device, such as a GaN or AlGaN device is described. In one example, a method to form the structure includes providing a substrate including gallium nitride material, forming an insulating layer over a surface of the substrate, forming an opening in the insulating layer to expose a surface region of the substrate, depositing a barrier metal layer over the insulating layer and onto the surface region of the substrate through the opening, and depositing a conducting metal layer over the barrier metal layer. In one case, the barrier metal layer includes a layer of tungsten nitride. The layer of tungsten nitride is deposited over the insulating layer and onto the surface region of the substrate using atomic layer deposition.