Ohmic contacts to CVD diamond with boron-doped $\delta$ layers

Various methods of the formation of ohmic contacts to CVD diamond epitaxial structures with boron doped delta layers ($\delta$-layers) are investigated. In the first approach, an additional thin, heavily doped layer was formed on the surface of the diamond film, to which the ohmic contact was formed. Then, the surface $p^+$-layer between the contact pads was etched out, so the current flow in the structure occurred only through the buried $\delta$-layer. In the second approach, doped diamond was selectively grown in contact windows under the mask of metal after preliminary etching the undoped diamond layer (cap) to the $\delta$-layer. In this case, the heavily doped $p^+$-layer will form a contact to the $\delta$-layer. These approaches are differs by conditions of applicability, the complexity of manufacturing technology, the value of contact resistance. So they can be used to solve tasks in which different quality of contacts is required, such as the formation of transistor structures or test cells for measuring electrophysical characteristics.