【International Papers】On Ga₂O₃ Self-Switching Nano-Diodes

      Researchers from the King Abdullah University of Science and Technology (KAUST) have published a dissertation titled "On Ga₂O₃ Self-Switching Nano-Diodes" in Advanced Electronic Materials.

Background

      Beta-phase of Gallium Oxide (β-Ga₂O₃) has garnered significant attention in recent years as a potential candidate for next-generation power electronics due to its unique material properties and suitability for mass production. It possesses an ultra-wide bandgap of ≈4.8 eV, a high critical electric field of ≈8 MV cm⁻¹, and has a scalable low-cost substrate growth functionality. Consequently, β-Ga₂O₃ based devices are expected to outperform their SiC and GaN counterparts for certain applications. Power diodes based on β-Ga₂O₃ have already surpassed the 1-D unipolar limit of SiC and GaN.

      Now, diodes are an integral part of most of the power converter circuits. While some diodes are used as switches, others are used to prevent hard saturation of transistors and protection of circuits from voltage spikes. Talking about β-Ga₂O₃, the majority of the β-Ga₂O₃ diodes developed so far are predominantly Schottky barrier diodes and p-n junction diodes. Interestingly, β-Ga₂O₃ photodiodes are also emerging as a promising candidate for deep ultraviolet (deep-UV) photodetection.

Abstract

      In this work, a Ga₂O₃ self-switching nano-diode (SSND) fabricated on a sapphire substrate is presented. Unlike previous SSND studies that primarily focused on rectification, this work explores additional device characteristics, including breakdown voltage and photodetection functionality. The diode exhibits increased current with the increase in the relative permittivity (κ) of the device trenches, and under UV illumination. Devices with increased κ achieve a high current density of ≈10 kA cm⁻², a rectification ratio of ≈10⁴, and a specific on-resistance as low as 0.29 mΩ cm². They also exhibit a breakdown voltage greater than 100 V, and a maximum power figure-of-merit of 35.46 MW cm⁻². Moreover, under 240 nm light illumination, the diodes showed a responsivity close to 10⁴ A W⁻¹. These initial results demonstrate the potential of the SSNDs toward monolithic Ga₂O₃ circuits that are currently under extensive investigation for various applications.

Conclusion

      In conclusion, this work shows the potential of β-Ga₂O₃ SSNDs toward providing multiple functionalities. β-Ga₂O₃ SSNDs exhibited a high current density of ≈10 kA cm⁻² and an extremely low specific R_on,sp below 0.8 mΩ cm², with a minimum of 0.29 mΩ cm², comparable to state-of-the-art diodes fabricated on native β-Ga₂O₃ substrates. The SSNDs exhibited a V_BR of ≈109 V and PFOM of 35.46 MW cm⁻². Moreover, SSNDs showed photo-response to deep-UV light with responsivity close to 10⁴ A W⁻¹ under 240 nm light illumination at 15 V. Therefore, β-Ga₂O₃ SSNDs are thought to provide multiple promising functionalities in monolithically integrated future β-Ga₂O₃ circuits.