第659回レーザー科学研究所コロキウム

●日時(Date):
2025年 11月 17日 13時 30分～ 14時 30分

○場所(Place):
レーザー科学研究所 研究棟4F 大ホール

●講演者(Speaker):
Prof. James C. M. Hwang (Cornell University)

○題目(Title):
Ordinary and Extraordinary Permittivities of 4H SiC at Different Millimeter-Wave Frequencies and Temperatures

●概要(Abstract):
Hexagonal semiconductors such as 4H SiC have important high-frequency, high-power, and high-temperature applications. The applications require accurate knowledge of both ordinary and extraordinary relative
permittivities, ε_perp and ε_parallel, perpendicular and parallel, respectively, to the c axis of these semiconductors. However, due to challenges for suitable test setups and precision high-frequency measurements, little reliable data exists for these semiconductors especially at millimeter-wave frequencies. This talk reports ε_perp and ε_parallel of high-purity semi-insulating 4H SiC from 55 to 330 GHz, as well as their temperature dependence enabled by improving the measurement precision to two decimal points. For example, at room temperature, real ε_perp and ε_parallel are constant at 9.77 ± 0.01 and 10.20 ± 0.05, respectively. By contrast, the ordinary loss tangent increases linearly with the frequency f in the form of (4.9 ± 0.1) × 10^{−16} f. The loss tangent, less than 1 × 10^{−4} over most millimeter-wave frequencies, is significantly lower than that of sapphire, our previous low-loss standard. Finally, both ε_perp and ε_parallel have weak temperature coefficients on the order of 10^{−4} /°C. The knowledge reported here is especially critical to millimeter-wave applications of 4H SiC, not only for solid-state devices and circuits, but also as windows for high-power vacuum electronics.

○連絡先(Contact Person):
中嶋 誠