Simulation Study of High Breakdown Voltage GaN Current Aperture Vertical Electron Transistor With Graded AlGaN Buffer Layer for Power Switching Applications

A novel current aperture vertical electron transistor with a graded AlGaN buffer layer is proposed and numerically investigated to enhance the breakdown capability of gallium nitride vertical devices for power switching applications. Compared with the conventional structure, the proposed device improves the electric field distribution in the buffer region, resulting in a more uniform field profile and a significant increase in breakdown voltage from 529.1 to 656.2 V, an improvement of about 24%. At the same time, the specific on‐resistance increases only slightly from 0.81 to 0.83 mΩ cm ² , while the maximum saturation current remains nearly unchanged. The influences of aperture width and buffer composition profile are also examined, showing that the design provides a better balance between breakdown performance and conduction capability after optimization. In addition, the graded buffer has little effect on input capacitance but reduces output capacitance, which is favorable for high‐frequency operation. These results indicate that the proposed device is a promising candidate for high‐voltage, low‐loss, and radio‐frequency GaN applications.