【Member News】 Industry-Leading Breakthrough! Shenzhen Pinghu Laboratory Achieves Dual Advances in Gold-Free Low-Resistance Ohmic Contact and Atomic-Scale Surface Planarization of Gallium Oxide

      Recently, the Fourth-Generation Semiconductor Research Team and New Technology Engineering Department of Shenzhen Pinghu Laboratory announced major progress in gallium oxide surface planarization and gold-free ohmic contact technology. Based on Ga₂O₃ epitaxial wafers grown by metal-organic chemical vapor deposition (MOCVD), the team achieved a specific contact resistance of 8E-7 Ω·cm² using a gold-free process, while also developing a novel surface planarization technique that reduced the root-mean-square (RMS) surface roughness of Ga₂O₃ to 0.107 nm. Both key metrics have reached industry-leading levels, providing critical support for the independent development and industrialization of fourth-generation semiconductors in China.

      Gallium oxide is a globally prioritized ultra-wide bandgap semiconductor material, featuring high breakdown voltage, high-temperature tolerance, and high-power capability. It is considered an ideal candidate for next-generation high-power electronic devices. However, two long-standing bottlenecks have constrained its transition to mass production: first, electrode contacts traditionally rely on costly gold (Au), which suffers from poor thermal stability; second, epitaxial wafer surfaces are relatively rough, leading to defect formation and electric-field crowding, which undermines device reliability. The Shenzhen Pinghu Laboratory team has now addressed both challenges simultaneously.

PART 01

Gold-free Ohmic Contact Process: Eliminating Gold Electrodes, Cutting Costs by 90%, Improving Stability

      Ohmic contact engineering for Ga₂O₃ has long depended on Au-based systems. Developing Au-free ohmic contacts is therefore a key step toward scalable manufacturing and technological independence. While traditional gold-based contacts can reduce contact resistance to some extent, they suffer from critical limitations such as high-temperature diffusion, poor thermal stability, high cost, and process incompatibility, all of which hinder performance and large-scale production.

      By adopting a multilayer stack design using non-precious metals and interface engineering, the team successfully achieved a specific contact resistance of 8E-7 Ω·cm², which is even lower than the ~1E-6 Ω·cm² level of conventional gold-based processes. At the same time, the new approach avoids major process bottlenecks, and reduces electrode material cost by more than 90%.

Simplified explanation:
      Think of it as building a “low-resistance superhighway” for electricity. A Ga₂O₃ power device is like a high-power “electrical heart,” and electrodes are the blood vessels that allow current to flow in and out smoothly.

      Previously, these electrodes had to be made of gold—expensive, thermally unstable, and unsuitable for mass production.

      Now, Shenzhen Pinghu Laboratory replaces gold with common non-precious metals and uses a layered “building-block” structure to create a wider, smoother, and more heat-resistant current pathway. The result: extremely low electrical resistance, dramatically reduced cost, and improved thermal stability—enabling scalable, reliable manufacturing.

PART 02

Surface Planarization of Ga₂O₃: Turning “Rough Sandpaper” into an Atomic-Scale Mirror

      Surface roughness is a critical parameter for evaluating both Ga₂O₃ substrates and homoepitaxial layers. Due to strong morphological inheritance during epitaxial growth, any surface irregularities on the substrate are directly transferred to the epitaxial layer and further amplified. Rough surfaces also introduce numerous dangling bonds and interface defects, increasing interface trap density. In addition, microscopic protrusions can cause local electric-field crowding, leading to premature device breakdown.

      To address this issue, the research team developed a new planarization process that reduced the RMS surface roughness of Ga₂O₃ epitaxial wafers to 0.107 nm—more than six times smoother than the initial state—achieving near-atomic-level flatness.

Simplified explanation:
      It is like performing “ultra-precision polishing” on a semiconductor surface.

      If Ga₂O₃ devices are like high-speed rail systems, then a rough surface is like uneven tracks full of bumps and pits—leading to instability, energy loss, or even failure.

      The new process transforms the surface from a rough “sandpaper-like texture” into an atomic-scale mirror. Electrons can now travel smoothly without scattering or local field concentration, resulting in higher stability, higher breakdown voltage, and longer device lifetime.

Conclusion

      These two breakthroughs together complete a key link from Ga₂O₃ materials to functional devices. They significantly enhance device performance and reliability, laying a solid foundation for large-scale applications in high-power electronics such as new energy systems, rail transportation, and smart grids.

      With continued advancement of gold-free contact technology and ultra-flat surface engineering, Ga₂O₃ is moving closer to commercialization, accelerating the global deployment of fourth-generation semiconductor technologies.