A reaction model explaining (i) the hydrogen-mediated transformation of the vacancy-oxygen (V O) center into a vacancy-oxygen-hydrogen center (V OH * ), with an energy level at 0.37 eV below the conduction-band edge (E c ), and (ii) the passivation of the divacancy center is presented. V OH * dissociates with a rate of 2 × 10 −5 s −1 at 195 • C, causing V O to recover after long duration (>10 4 min), while a similar evolution occurs at 300 • C on a time scale of the order of 10 min. The diffusivity of the monatomic hydrogen used in the model agrees closely with the established values for the diffusivity of protons. After the recovery of V O, further annealing at higher temperatures and/or longer durations transforms V O into the "ordinary" vacancy-oxygen-hydrogen center with an energy level at E c − 0.32 eV (V OH). V OH is subsequently transformed into V OH 2 . For temperatures above 250 • C, two additional hydrogen-related levels occur (∼ 0.17 and ∼0.58 eV below E c ) with a one-to-one ratio and a possible association with different charge states of a V 2 OH center is discussed.

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A commercially available InGaAs p-in photodiode chip has been custom packaged and high-speed operated in liquid helium. The photodiode was driven by light pulses using a dc-biased 1310-nm laser, a Mach-Zehnder modulator, and a return-to-zero pulse pattern generator up to 15 GHz clock frequencies, which produced pulse widths down to 77 ps and maximum peak current heights above 10 mA. With the prospect of using this photodiode assembly to operate pulse-driven Josephson junction arrays for ac voltage realization, pulsation modes with constant pulse width and varying pulse density were applied to the diode, which resulted in consistent pulse shapes for bit rates as high as 7.5 Gb/s. This could yield realizable peak voltages as high as 15.525 µV per Josephson junction. Time-lapse pulse measurements were performed over the span of 90 min, which demonstrated good waveform stability. Using the measured current waveforms, the behavior of a typical Josephson junction was simulated according to the Stewart-McCumber model, which resulted in an operational margin of 2 mA for the first Shapiro step.

Electronic properties and thermal stability of interfacial states between indium tin oxide (ITO) and monocrystalline silicon (Si) have been investigated. ITO films with thicknesses of about 300 nm were deposited by dc magnetron sputtering on n- and p-type (100) Si at room temperature. The samples were then annealed for 30 min at different temperatures in the range 100–600 °C, and the ITO-Si junction was found to exhibit rectifying behavior. Current-voltage (IV), capacitance-voltage (CV), and deep-level transient spectroscopy (DLTS) measurements have been used to electrically characterize the ITO-Si interface. DLTS measurements on p-type Si samples reveal a dominant hole trap at around 0.37 eV above the valence band edge. In the n-type samples, a broad band of electron traps occur in the range 0.1-0.2 eV below the conduction band edge. These electron traps display wide DLTS peaks, indicating a band of electronic energy levels rather than well-defined states originating from isolated point defects. All the traps in both the p- and n-type samples are found to be located near the ITO-Si interface. Investigations of the thermal stability of the observed electronic states show that the dominant hole trap anneal out after 30 min at 250 °C, while the dominant electron traps can be stable up to 500 °C. IV and DLTS measurements demonstrate a clear correlation between the annealing of the dominant electronic states and increase in the junction rectification.