Professor/RARA Fellow Kentaro Kaneko of the Research Organization of Science and Technology, Ritsumeikan University, and Patentix Inc. (Location: Kusatsu City, Shiga Prefecture/CEO: Toyosuke Ibi) have succeeded in jointly developing the rutile-structured germanium dioxide (r-GeO₂) film, which is prominent as a next-generation semiconductor material, on silicon carbide (SiC) using the Phantom SVD method for the first time in the world.

Patentix Inc. is a semiconductor deep tech venture originating from Ritsumeikan University in December 2022. Prof. Kaneko, who is also a co-founder and CTO of Patentix Inc., developed a novel power semiconductor material of r-GeO₂. Patentix Inc. conducts research and development for r-GeO₂ semiconductor substrates and power devices.

These research results were presented by Yuri Shimizu (Director of Patentix Inc./Graduate School of Science and Engineering) at the Fall Meeting of Europe’s largest material research society, “European Materials Research Society (E-MRS),” held in Warsaw, Poland from September 18th to 21st, 2023. While low thermal conductivity of substrates has been an issue for the development of oxide semiconductor power devices, the significant findings indicate the possibility of overcoming it using SiC, which has excellent heat dissipation properties. In addition, Prof. Kaneko, gave an invited talk on research achievements thus far with regard to r-GeO₂ and its future prospects.

1. Overview

As rutile-structured germanium dioxide (r-GeO₂) has a larger band gap than silicon carbide (SiC) and gallium nitride (GaN), r-GeO₂ transistors and diodes are expected to be equipped with excellent power device characteristics including high breakdown voltage, high output current, and high power conversion efficiency. Japan leads the world in development of r-GeO₂ power devices, and Patentix Inc. has been conducting research and development for r-GeO₂ epi-wafers since its establishment in December 2022.

Furthermore, Patentix Inc. has been developing new fabrication method of Phantom SVD. Its crystal growth mechanism is different from the conventional mist CVD method and it enables a safer and more secure thin film synthesis.

2. Findings and future plans

Ritsumeikan University and Patentix Inc. have succeeded in jointly developing the rutile-structured germanium dioxide (r-GeO₂) film on SiC crystal using the Phantom SVD method for the first time in the world.

The research results were presented at the Fall Meeting of Europe’s largest material research society, “European Materials Research Society (E-MRS),” held in Warsaw, Poland from September 18th to 21st, 2023 by Yuri Shimizu (Director of Patentix Inc./Graduate School of Science and Engineering). While low thermal conductivity of substrates has been an issue for the development of oxide semiconductor power devices, the significant findings indicate the possibility of overcoming it using SiC, which has excellent heat dissipation properties.

Ritsumeikan University and Patentix Inc. will evaluate r-GeO₂ thin films’ electrical characteristics and defects inherent in the films, and continue developing a high-quality r-GeO₂ epitaxial film formation technology.

Photo: Rutile structure r-GeO₂ formed on Si(111)/3C-SiC(111). The unfabricated area on the far left is a trace of masking for film thickness measurement. Structure: A thin film of 3C-SiC (111) was formed on the Si(111) substrate. Then, an r-GeO₂ film was formed on the 3C-SiC (111).