The MSM structures based on high-quality 1.6 μm in thick α-Ga ₂ O ₃ films grown by the halide vapor phase epitaxy with Ti/Ni interdigital contacts were developed for detection of short-wave ultraviolet (UVC) radiation. The spectral dependences of responsivity, external quantum efficiency and detectivity of MSM structures based on α-Ga ₂ O ₃ were studied in the wavelength range of 205-260 nm. The responsivity, the external quantum efficiency and the detectivity are 7.19×10 ⁴ A×W ^-1 , 3.79×10 ⁵ arb.un. and 1.12×10 ¹⁸ Hz ^0.5 ×cm×W ^-1 , respectively, for structures with an interelectrode distance of 30 μm at an applied voltage of 10 V and exposure to radiation with a wavelength of 235 nm. The high values of the photoelectric characteristics were caused by the manifestation of an internal gain of the photoresponse due to the self-localization of holes in α-Ga ₂ O ₃ . The prospects of researches to develop UVC radiation detectors for wireless UVC communication were shown.

The results of theoretical and experimental investigation of charge carrier transport in avalanche S-diodes based on π-ν-n and π-n structures are presented. High-ohmic layers of the diodes were made by diffusion of deep chromium and iron acceptors into n-GaAs. It is shown that recharge of the deep acceptors in the avalanche regime should lead to expansion of the space charge region into the π-layer and formation of step-type current-voltage characteristics rather than the S-type. It has been found experimentally that the switching of the S-diode is superfast (the time of switching is less than the transient time of the carriers through the active region). The obtained results are in contradiction with the earlier proposed mechanism of deep-level recharging. Thus, this mechanism has been revised. The comparison of the obtained results with the literature data allows one to find the only mechanism of superfast switching, which is associated with generation of collapsing field domains due to the Gunn effect under the avalanche breakdown condition. According to the experiment, the switching time of S-diodes depends on the applied voltage and the type of the deep-level impurity. The S-diodes can operate in relaxation oscillator and sharper circuits. The use of the S-diodes in a sharper circuit with a moderate voltage rate of 1011 V/s allows generating the voltage pulses with amplitude of 700 V and a rising edge of 250 ps at a load of 50 Ω.

Indium tin oxide thin films were deposited by magnetron sputtering on ceramic aluminum nitride substrates and were annealed at temperatures of 500 °C and 600 °C. The structural, optical, electrically conductive and gas-sensitive properties of indium tin oxide thin films were studied. The possibility of developing sensors with low nominal resistance and relatively high sensitivity to gases was shown. The resistance of indium tin oxide thin films annealed at 500 °C in pure dry air did not exceed 350 Ohms and dropped by about 2 times when increasing the annealing temperature to 100 °C. Indium tin oxide thin films annealed at 500 °C were characterized by high sensitivity to gases. The maximum responses to 2000 ppm hydrogen, 1000 ppm ammonia and 100 ppm nitrogen dioxide for these films were 2.21 arbitrary units, 2.39 arbitrary units and 2.14 arbitrary units at operating temperatures of 400 °C, 350 °C and 350 °C, respectively. These films were characterized by short response and recovery times. The drift of indium tin oxide thin-film gas-sensitive characteristics during cyclic exposure to reducing gases did not exceed 1%. A qualitative model of the sensory effect is proposed.

The structural and gas-sensitive properties of n-N SnO₂/κ(ε)-Ga₂O₃:Sn heterostructures were investigated in detail for the first time. The κ(ε)-Ga₂O₃:Sn and SnO₂ films were grown by the halide vapor phase epitaxy and the high-frequency magnetron sputtering, respectively. The gas sensor response and speed of operation of the structures under H₂ exposure exceeded the corresponding values of single κ(ε)-Ga₂O₃:Sn and SnO₂ films within the temperature range of 25–175 °C. Meanwhile, the investigated heterostructures demonstrated a low response to CO, NH₃, and CH₄ gases and a high response to NO₂, even at low concentrations of 100 ppm. The current responses of the SnO₂/κ(ε)-Ga₂O₃:Sn structure to 10⁴ ppm of H₂ and 100 ppm of NO₂ were 30–47 arb. un. and 3.7 arb. un., correspondingly, at a temperature of 125 °C. The increase in the sensitivity of heterostructures at low temperatures is explained by a rise of the electron concentration and a change of a microrelief of the SnO₂ film surface when depositing on κ(ε)-Ga₂O₃:Sn. The SnO₂/κ(ε)-Ga₂O₃:Sn heterostructures, having high gas sensitivity over a wide operating temperature range, can find application in various fields.

Pt/(100) β-Ga2O3 Schottky barrier diodes were fabricated using a plate cleaved from the crystal grown by Czochralski method. Their electroconductive and photoelectric characteristics were studied. The following values were obtained: the Schottky barrier height (1.69/1.62/1.74 eV), ideality coefficient (1.09/1.14), saturation current density (9.91 × 10–15 A/cm2), diode series resistance (7.98 kΩ), and net donor concentration [(1.8–2.4) × 1018 cm–3]. The diodes demonstrate a high rectification ratio of 1010 at an applied voltage of ± 1 V and a relatively low experimental value of the leakage current density ∼10–11 A/cm2. These structures are solar-blind and also capable of operating in self-powered mode. The diodes are highly sensitive to short-wave ultraviolet radiation with a wavelength λ ≤ 265 nm. The maximum values of responsivity (20.4 A/W), external quantum efficiency (1.2 × 104%), and detectivity (9.6 × 1015 Hz0.5 × cm × W–1) of diodes were registered under exposure to irradiation at λ = 210 nm and at applied voltage of −1 V. The responsivity and external quantum efficiency values in the self-powered operation mode were 12.3 A/W and 7.2 × 103%, respectively. The diodes showed low rise and decay times in self-powered operation mode for photodiode based on Ga2O3: 14 and 30 ms, respectively.

The article is concerned with a detailed switching delay effect exhibited by avalanche S-diodes--superfast GaAs closing switches doped with deep Fe centers. The current and voltage time dependences are simulated in a simplified generator. The dynamic electric field and charge profiles in the structures are calculated. This article describes an impact that Fe capture cross sections of free charge carriers have on delayed switching. The simulation results show that delayed switching is associated with deep center recharging in a double injection mode due to three different processes. There are two different delay mechanisms to be herewith distinguished. A delay effect is experimentally viewed to control the dynamic switching voltage (and the avalanche breakdown voltage) using constant voltage adjustment capability enabled by a triggering circuit supply. The authors demonstrate the way it is possible to adjust the amplitude of current nanosecond pulses in the range of 20-45 A through a lidar transmitter circuit with a semiconductor laser and nonoptimized S-diode. The findings are consistent with the results of numerical simulation.