Vertical GaN P-N Power Diodes with Ion Implantation Based Edge Termination

Semiconductor-based power electronics play an important role in power consumption since a significant fraction of the consumed power is lost as heat during the conversion. GaN is the most promising material to reduce these losses due to its favorable properties, including large band gap, high breakdown electric field, high thermal conductivity, and excellent transport properties. However, the power conversion efficiency and current drivability of power diodes is limited by suboptimal edge termination due to field crowding. Therefore, this work focuses on the design, fabrication, and evaluation of highly effective edge terminations for high power vertical GaN p-n diodes. In this work, we present the design and optimization of ion implantation-based edge termination techniques. To overcome the drawbacks of traditional junction termination extension (JTE), a novel fabrication of triple-zone JTE structure was proposed. Numerical simulations suggest that this design offers improved blocking performance and wider fabrication process window. To verify this performance potential, vertical GaN p-n diodes with both conventional single-zone and proposed triple-zone JTE structures have been fabricated. As projected, the triple-zone devices offer a wider window for fabrication processing to achieve high breakdown voltage compared to single-zone devices. The experimental results prove that the proposed triple-zone JTE structure is effective in enlarging the process window and allowing for more variation and non-uniformity of p-GaN epi-layer while maintaining high voltage blocking capability. Furthermore, the breakdown voltage of the diodes displayed a positive temperature coefficient, indicating that the devices support material-limited avalanche breakdown. We also introduced a novel approach for manufacturing vertical GaN p-n diodes with a triple-zone step-graded JTE by a simplified single nitrogen ion implantation process. This streamlined method is more accessible and cost-effective while still retaining the advantages of the triple-zone design. These advancements have significantly improved the overall efficiency of the fabrication process of GaN-based power diodes.