Sapphire (α-Al2O3) is widely used for window materials and substrates for blue LEDs, etc., because large-area crystals of 8-inch size can be obtained, it is low cost and high quality, and yet it is transparent to visible light due to its large band gap (~9 eV). Sapphire is known as a good insulator, and there have been no examples of electricity flowing through it at room temperature.

　In this study, a highly concentrated Si-doped Al2O3 film was grown by molecular beam epitaxy and heat-treated at 1400°C under inert gas to successfully conduct electricity at room temperature. The resistivity was 166 Ωcm, which is classified as a semiconductor in terms of electrical conductivity.

　The demonstration of the conductive sapphire film has opened up the possibility of realizing a vertical device on a sapphire substrate, which has been difficult to achieve until now. In addition, new developments such as high-temperature, high-power, high-radiation resistant elements and vacuum ultraviolet elements can be expected.

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https://www.jsap.or.jp/docs/pressrelease/JSAP-2023autumn-chumoku-11.pdf
https://doi.org/10.35848/1347-4065/aca196