【International Papers】Unipolar β-Ga₂O₃ Pseudo-junction barrier Schottky diodes via Low-Cost magnesium diffusion process

      Researchers from the KAUST have published a dissertation titled "Unipolar β-Ga₂O₃ Pseudo-junction barrier Schottky diodes via Low-Cost magnesium diffusion process" in APL Materials.

Background

      Ultra-wide bandgap (UWBG) semiconductors have attracted significant attention as key materials for next-generation power electronics. Among these, beta-gallium oxide (β-Ga₂O₃) stands out due to its ultra-wide bandgap of ~4.8 eV, high breakdown field (~8 MV/cm), and cost-effective bulk substrate growth, making it a promising candidate for high-voltage power devices. Diodes are fundamental in power circuits, and Junction Barrier Schottky (JBS) diodes combine low turn-on voltage with enhanced breakdown voltage through p-type grids near the Schottky interface. However, the lack of reliable p-type β-Ga₂O₃ has driven exploration of alternatives such as p-type NiO_x, which faces issues including lower bandgap, lattice mismatch, and interface recombination. Recently, magnesium (Mg) diffusion has emerged as a method to create high-resistance electron-blocking layers, demonstrated in both GaN andβ-Ga₂O₃ devices. Existing approaches like Mg-doped Spin-on-Glass or high-temperature (>1000 °C) diffusion are complex and costly. This work proposes a low-cost, room-temperature compatible Mg diffusion technique directly into selected regions of β-Ga₂O₃ substrates to form high-resistance areas, enabling Schottky barrier diode (SBD) devices with enhanced breakdown voltage, reduced processing temperature, and simplified fabrication, providing a practical route for β-Ga₂O₃ JBS device development.

Abstract

      Beta Gallium Oxide (Ga₂O₃) Junction Barrier Schottky diodes possess excellent breakdown characteristics and efficiency, but the lack of p-type Ga₂O₃ has led to the use of alternative materials, such as NiO_x, which pose challenges regarding lattice mismatch and temperature stability. This work reports a unipolar Ga₂O₃ diode enabled by the magnesium (Mg) diffusion process to create high-resistance electron-blocking regions. The Mg diffusion process developed in this work uses a room temperature compatible chemical process followed by an 800 °C annealing step, which is lower compared to already reported methods in the literature. Therefore, the proposed method is thought to reduce the device processing temperature budget and hence cost. The resulting device achieves an I_on/I_off ratio of ∼10⁹, a knee voltage of ∼0.9 V, and a breakdown voltage of 596 V. In addition, it demonstrates stable operation from 100 to 500 K, highlighting its suitability for electronics operating across a broad temperature range.

Conclusion

      This work demonstrates a β-Ga₂O₃ SBD enabled by Mg diffusion into selected areas of the β-Ga₂O₃ substrate to create highly resistive regions. The proposed methodology offers a low-cost, silicon-free solution optimized for Mg diffusion. The fabricated SBD having Mg diffusion regions outperformed the regular SBD; the proposed diode offered a significant improvement in breakdown voltage without introducing any serious compromise in the ON-state characteristics. Finally, the proposed diode is shown to offer suitable performance over a wide range of temperature, making it a promising device for extreme harsh electronics.