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An improvement of the electroluminescence (EL) intensity of the CdF 2 /CaF 2 intersubband transition (ISBT) light-emitting structure is reported. In the ISBT active region, the precise control of crystal growth is strongly required. In this work, the hydrogenannealing surface flattening of Si substrates was employed to obtain a high quality active region to suppress non-radiative leakage current. A markedly flat surface was obtained in the 30-µm-wide trench bottom after hydrogen annealing. In the EL measurement of the device fabricated in the trench, the EL intensity was approximately 40 times stronger than that of the device without patterning and hydrogen annealing.

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Flux-flow-type Josephson oscillators consisting of epitaxial NbCN/MgO/NbCN junctions were fabricated and their current-voltage(1-V) characteristics were measured in various magnetic fields to evaluate their oscillation characteristics. On the I-V curve for a fabricated oscillator, clear current steps were observed up to 3mV, indicating that oscillation occurs up to 1.4THz. Using a theoretical model, available output power for the oscillator was calculated to be in the range from 20pW to 40pW in a frequency range from 5OOGHz to 1.2THz.