Topology optimization of JTE structure in vertical GaN power devices

This study applies a topology optimization approach to the design of a Junction Termination Extension (JTE), which is one of the edge-termination structures for vertical GaN power devices. Conventional parameter optimization requires independent tuning of the width, depth, and impurity concentration of the JTE region to achieve the desired breakdown voltage. As the number of target regions increases, the combinations of design parameters grow explosively. Consequently, severe constraints such as enforcing identical impurity concentrations across regions are often imposed, which substantially limit the design freedom. Focusing on the fact that a JTE structure can be represented as a dose distribution, we perform optimization with high design freedom using topology optimization. Since breakdown voltage correlates with the maximum electric field strength under reverse bias, we optimize the dose distribution to reduce the maximum electric field strength of the device. For a vertical GaN device biased at 900V in reverse, the proposed method reduces the maximum electric field strength by 12.5% compared with a structure obtained by parameter optimization.