Confirmation of p-type Schottky Barrier Diode Characteristics in Rutile Germanium Dioxide Thin Films with Ion-Implanted Acceptor Impurities

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　March 31, 2026

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　Patentix Inc.

Patentix Inc. (hereinafter referred to as "the Company") has confirmed p-type SBD characteristics by ion-implanting acceptor impurities into thin films of rutile germanium dioxide (r-GeO₂), a material for next-generation power semiconductors.

【Background】

Rutile germanium dioxide (r-GeO₂) is a candidate for next-generation power semiconductor materials, possessing a wider bandgap (4.68 eV) than silicon carbide (SiC) and gallium nitride (GaN). Furthermore, it has garnered significant attention in recent years due to theoretical predictions that it can achieve both p-type and n-type conductivity through impurity doping, a feat difficult with other ultra-wide bandgap semiconductor material candidates. However, the p-type conductivity of r-GeO₂ remains at the stage of theoretical prediction.

In July 2025, the Company reported obtaining C-V characteristics suggesting p-type conductivity in r-GeO₂ films into which acceptor impurities were introduced. On the other hand, further accumulated data is necessary for a definitive demonstration of p-type conductivity.

【Results】

This time, the Company fabricated r-GeO₂ thin films on rutile titanium dioxide (r-TiO₂)(001) substrates using its proprietary deposition technology, the Phantom SVD method. Acceptor impurities were introduced into the film through an ion implantation process, followed by activation annealing. Metal electrodes were formed on the surface of the r-GeO₂ film, and its electrical characteristics were evaluated. Figure 1 shows the appearance of the fabricated and evaluated sample. Cracks (fissures in the crystalline film) appeared on the surface of the r-GeO₂ film after activation annealing.

　　　　　　　Figure 1. (a) Appearance of the r-GeO₂ sample with implanted acceptor ions (b) Schematic cross-section

I-V and C-V characteristics were measured and evaluated between the two formed electrodes (a small circular electrode and a larger surrounding electrode). Figure 2 shows the I-V characteristics (a) and C-V characteristics (b).

　　　　　　　　　　　　Figure 2. (a) I-V characteristics and (b) C-V characteristics of the fabricated sample

The I-V characteristics show that a large current flows when a negative voltage is applied to the circular electrode, while current flows with difficulty when a positive voltage is applied (diode characteristics). This suggests that electrical conduction occurs in the r-GeO₂ film with holes as carriers (p-type conduction). Furthermore, as shown in Figure 2(b), p-type characteristics can also be confirmed from the C-V characteristics.

On the other hand, some test patterns formed on the same substrate did not show p-type characteristics, indicating that improvement in stability and reproducibility is an issue.

【Future Prospects】

Patentix will continue research and development towards the definitive verification of p-type conduction in r-GeO₂. In particular, confirming p-type conductivity through Hall effect measurements, measuring hole mobility, and achieving a pn junction remain the most critical challenges. Moving forward, the company aims to demonstrate p-type conduction in r-GeO₂ by improving crystal quality and exploring activation annealing conditions.

End