Thin-film corundum-structured gallium oxide (α-Ga2O3) Schottky barrier diodes (SBDs) were fabricated by growing α-Ga2O3 layers on sapphire substrates by the safe, low-cost, and energy-saving MIST EPITAXY® technique, followed by lifting off the α-Ga2O3 layers from the substrates. The SBDs exhibited on-resistance and breakdown voltage of 0.1 mΩ·cm2 and 531 V (SBD1) or 0.4 mΩ·cm2 and 855 V (SBD2), respectively. These results will encourage the future evolution of low-cost and high-performance SBDs with α-Ga2O3.

We study the universal relationship between the hot-spot size and the intensity of terahertz emission from intrinsic Josephson junctions by dynamically controlling the temperature distributions in mesas of Bi 2 Sr 2 CaCu 2 O 8þδ . The uniform current bias leads to a significant increase in local temperature compared to the nonuniform current bias. The thermal response of emission differs between the high-and low-bias regimes. We find a strong positive correlation between the emission intensity and the volume of the superconducting parts in the emitting stack. We identify the remarkable increase in the emission intensity by up to 20% by eliminating the excess Joule heat from the mesa.

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Interlayer tunneling spectra, the Josephson critical current density J c , and the normal tunneling resistance have been measured simultaneously for intrinsic Josephson junctions of Bi 1.9 Pb 0.1 Sr 2 CaCu 2 O 8+δ (BiPb2212) in the underdoped region using a small mesa structure (S = 1 × 1 μm 2) and a short-pulse technique. J c was significantly enhanced when Bi was partially replaced with Pb. By comparing J c with the value estimated by the Ambegaokar-Baratoff formula, it was found that superfluid density doubles in the Pb-containing sample. In addition, Pb raises the superconducting coherence peak without changing the value of the superconducting gap. Based on a model that accounts for the inhomogeneity of in k space, we argue that the superfluid density increases because Pb substitution increases the homogeneity of (k).

We observe continuous terahertz-wave emission from a stack of intrinsic Josephson junctions made of slightly Pb-doped Bi 2 Sr 2 CaCu 2 O 8 d + . We investigate how Pb doping affects the c-axis current-voltage and emission characteristics. The terahertz emission spectra are measured by Fourier-transform infrared spectroscopy and reveal that the emission frequency is remarkably increased by Pb doping, an effect that we attribute to cavity resonance.