【Member News】High-quality 4-inch gallium oxide single crystal is successfully prepared via casting process by research team of Hangzhou International Science and Technology Innovation Center of Zhejiang University

      In the busy semiconductor materials research room, white gallium oxide powder sand tower, and silently grows in the single crystal growth furnace. The gallium oxide substrate and epitaxial wafer processed by it can be made into various kinds of power devices, which have unlimited prospects in new energy vehicles, rail transit, renewable energy power generation and other fields, and are expected to greatly reduce energy consumption.

      Recently, Hangzhou Garen Semi co., LTD., joint hands with Advanced Semiconductor Research Institute of Zhejiang University Hangzhou Global Scientific and Innovation Center (hereinafter referred to as the Center) , Silicon and Advanced Semiconductor Materials National Key Laboratory, using casting method successfully prepared high quality 4-inch gallium oxide single crystal, and completed the technology breakthrough of 4-inch gallium oxide wafer substrate.

gallium oxide single crystal of 1 inch, 2 inch, 4 inch

      This project was funded by Zhejiang Province 2023 "Bellwethers" R & D Program and supported by "5213" Excellence Program in Xiaoshan District, Hangzhou. Casting method is a new melt technology suitable for gallium oxide gallium oxide single crystal growth, which is independently developed by the team of Academician Yang Deren, the chief scientist of the Center. The gallium oxide wafer produced by this method has two significant advantages. First, due to a new try of the melt method being adopted, the use of precious metal iridium is significantly reduced, so that the growth process of gallium oxide is not only simpler and more controllable, but also the cost is lower, and has a broader industrialization prospect; Second, the gallium oxide grown by this method is columnar crystal, which can meet the needs of different use.

      "The price of iridium is thousands of yuan per gram, which is more precious than gold. But the mainstream method of growing gallium oxide crystal using melt crucible and accessories need a large amount of precious metal iridium, so it has been difficult to reduce the substrate cost in the past.” said Professor Zhang Hui, the team leader, " The method we adopted has significantly reduced the use of iridium, with lower costs and practical significance for industrialization.”

      Solid-liquid interface instability of Gallium oxide, high density of dislocations caused by thermal shock, regulation of the temperature gradient, crystal cleavage and so on....actually, the casting method has also encountered many problems in the research and development process. We worked in relays and modified the scheme. After hundreds of experiments, the team finally optimized the casting process and broke through various technical problems in growth and processing.

X-ray rocking curves and atomic force microscopy plots

      According to the wafer test analysis, the crystal quality and processing technology also remain at the product level standard. The half-height width of high-resolution X-ray rocking curve is less than 100 arcsec and the diffraction peak is uniformly symmetrical, indicating good crystal quality. The processed wafer was confirmed by AFM test, and the surface roughness was less than 0.5 nm.

      As early as last May, the Center successfully broke through the 2-inch growth technology and prepared a 2-inch diameter gallium oxide wafer, laying a solid foundation for the mass production of gallium oxide. In the future, the team will continue to carry out independent innovation work, gradually break through the larger size and higher quality of gallium oxide substrate, and promote the high-quality development of gallium oxide industry.