High breakdown voltage vertical GaN p-n junction diodes using guard ring structures

New guard ring structures were adopted to increase the breakdown voltages of the vertical GaN p-n diodes. With this structure, a voltage drop occurs in the guard ring portions by inserting resistance devices between the guard ring portions and the main p-n diode portions, and it is possible to attain higher breakdown voltages by the voltage drop at the most sensitive outer region of the diodes. By adopting this structure, the breakdown voltages of about 200 V has been improved compared with the normal circular p-n diodes.