Signing of Letter of Intent to Conduct Joint Research on Diamond Device Materials with Honda R&D Co., Ltd.

1. Introduction Development of various diamond devices is accelerating, and the realization of power devices for use in electric vehicles and similar applications—overcoming the limitations of existing devices—is eagerly anticipated. Honda R&D Co., Ltd. (hereinafter "Honda R&D") has already been advancing this development: in March 2025, it published a paper jointly with the National Institute of Advanced Industrial Science and Technology (AIST) demonstrating the potential of high-current devices, and in February 2026 it established the "Honda R&D–AIST Diamond × Electronics Collaborative Research Laboratory" as an open-innovation hub for diamond semiconductors. Our company has long supported the development of various diamond devices by commercializing diamond substrates, wafers, and related products. In February 2025, we commercialized the world's largest 30×30 mm single crystal, and in April of the same year we began selling 1-inch wafers (25 mm diameter). As more research institutions join the field and device structures grow increasingly diverse, we have also commercialized low-resistance substrates and substrates with various epitaxial layers. As a result, our company now offers the world's broadest lineup of products for diamond device development. Against this backdrop, our company and Honda R&D have agreed to begin exploring a joint research arrangement, with the goal of accelerating development toward the practical application of diamond power devices. 2. Key Points of the Basic Agreement Diamond devices, when applied to power devices for future use in electric vehicles and similar applications, are expected to improve fuel efficiency through enhanced fundamental performance, and they are free from the resource-scarcity concerns associated with gallium nitride and similar materials. However, numerous technical challenges currently remain in using diamond as a semiconductor device material. Furthermore, introducing a new semiconductor material into automotive applications requires lengthy development periods involving long-term durability testing. It is also desirable to use already-established device fabrication processes for automotive semiconductor production; in the case of diamond, materials development must advance first, or device development itself cannot proceed smoothly. The letter of intent signed on this occasion aims to explore the conclusion of a joint research agreement focused primarily on enlarging diamond wafer size and improving wafer quality, so that mass-production considerations can be incorporated into future device development. Resolving these challenges will enable mass production of devices using existing semiconductor processes and pave the way for manufacturing diamond devices. By advancing the joint research, the path to future mass production will become clear, and the roadmap for subsequent device development will be defined. As a result, it is expected that a concrete development plan for practical automotive power devices can be formulated and development can move into a new phase. 3. Next Steps Based on This Agreement In accordance with this agreement, we aim to conclude a formal joint research contract with Honda R&D by the end of August 2026. Following execution of that contract, development will begin using our existing facilities, with plans to sequentially introduce newly required equipment and build the necessary experimental infrastructure. 4. Our Future Plans In the diamond wafer development roadmap announced on November 28, 2024, our company outlined a plan to expand wafer size from 2-inch to 4-inch. Development of 2-inch wafers is actively ongoing, and our commitment to realizing these products remains unchanged. We also plan to broadly market the various products that can be commercialized through this joint research, with the goal of promoting the widespread adoption of diamond devices. As a leading supplier of the various types of diamond materials required for diamond device development, our company will continue to maintain a globally leading position, promote standardization of our products, and fulfill our role in advancing the early practical application of diamond devices. ■ Inquiries regarding this matter: EDP Co., Ltd. — Sales Department 4-6-3 Kamishinden, Toyonaka, Osaka 560-0085, Japan (Email) edp.info@d-edp.jp