Success in Depositing Rutile-type Germanium Dioxide (r-GeO₂) Single-Crystal Film on Si Substrate

May 13, 2026

Patentix Inc.

Patentix Inc. (hereinafter referred to as "the Company"), in collaboration with JTEKT THERMO-SYSTEM Co., Ltd., has developed and manufactured a new 6-inch compatible deposition apparatus, successfully depositing a single-crystal film of rutile-type germanium dioxide (r-GeO₂), a next-generation power semiconductor material, onto a Si substrate.

Background

Rutile-type germanium dioxide (r-GeO₂) is a next-generation power semiconductor material with a larger bandgap (4.68eV) than silicon carbide (SiC) and gallium nitride (GaN), and is expected to reduce energy loss associated with power conversion.

For the practical application of r-GeO₂ power devices, it is essential to realize large-diameter r-GeO₂ substrates of 6 inches or more that are compatible with power device production lines. The Company has been advancing research and development in deposition technology, including developing its unique deposition method suitable for r-GeO₂, called the PhantomSVD method, and achieving the deposition of single-crystal r-GeO₂ films across the entire surface of r-TiO₂ substrates. In a press release in July 2025, the Company announced its success in fabricating r-GeO₂ films on Si substrates, and this time, it has succeeded in depositing the r-GeO₂ single-crystal film indispensable for power device applications.

Achievements

In the previous announcement, the "foundational technology" of depositing r-GeO₂ on Si substrates was established. However, to realize power devices that require high voltage without breakdown and no leakage current in the OFF state, it is essential to fabricate devices using r-GeO₂ single-crystal films where atoms are regularly arranged.

This time, the Company jointly manufactured a new 6-inch substrate-compatible deposition apparatus with JTEKT THERMO-SYSTEM Co., Ltd., adopting its independently developed deposition method (named the "Chimney method"). By using the manufactured "Chimney method" deposition apparatus, the Company succeeded in depositing a single-crystal r-GeO₂ film on a Si substrate, which has a significantly different crystal structure and lattice constant from r-GeO₂.

As shown in the figure, analysis by the Electron Backscatter Diffraction (EBSD) method confirmed that the entire r-GeO₂ film deposited on the Si substrate has the same crystal orientation, meaning the successful heteroepitaxial growth of a single-crystal r-GeO₂ film on the Si substrate.

Results of EBSD Analysis

1. **Uniformity of Crystal Orientation**: Confirmed that crystal axes are highly aligned throughout the film, with no grain boundaries typically seen in polycrystalline structures. 2. **High Inverse Pole Figure (IPF) Mapping Accuracy**: Shows uniform hue across the entire measured region, indicating high crystal quality.

The Company adopts a conductive buffer layer to realize the deposition of r-GeO₂ crystal films on Si substrates, which have significantly different crystal structures. By using a conductive buffer layer, it is expected that a vertical device structure, common for power devices, can be easily realized.

By combining the conductive buffer layer technology suitable for vertical devices with the accumulated r-GeO₂ deposition technology, the Company aims to realize "GeO₂ on Si substrate" and implement next-generation semiconductor substrate materials that enable both low manufacturing costs and high-performance vertical power devices in society.

Future Outlook

To achieve early market entry, Patentix Inc. plans to prototype large-diameter 6-inch r-GeO₂ substrates suitable for power device production lines using this single-crystal r-GeO₂ deposition technology. Additionally, the Company will improve the quality of r-GeO₂ single-crystal films and proceed with prototyping and evaluating fully vertical Schottky Barrier Diodes (SBDs) and Field-Effect Transistors (FETs) using GeO₂ on Si substrates.

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