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.

Resistive metal/β-Ga₂O₃/metal structures with different interelectrode distances and electrode topologies were investigated. The oxide films were deposited by radio-frequency magnetron sputtering of a Ga₂O₃ (99.999%) target onto an unheated sapphire c-plane substrate (0001) in an Ar/O₂ gas mixture. The films are sensitive to ultraviolet radiation with wavelength λ = 254. Structures with interdigital electrode topology have pronounced persistent conductivity. It is shown that the magnitude of responsivity, response time τ_r, and recovery time τ_d are determined by the concentration of free holes p involved in recombination processes. For the first time, it is proposed to consider hole trapping both by surface states N_ts at the metal/Ga₂O₃ interface and by traps in the bulk of the film.

In this report, we consider the effect of radiation with a radiation energy below the β-Ga2O3 band-gap on the photoelectric characteristics of ultraviolet (UV) radiation detectors based on gallium oxide thin films. The gallium oxide film was deposited by the radio frequency magnetron sputtering. Interdigital Ti/V electrodes were formed with an inter electrode distance d = 30 μm. The structures exhibit high value of photocurrent under irradiation with wavelength of λ = 254 nm and intensity of 780 μW/cm2. The detectors exhibit persistent photoconductivity after exposure to UV radiation. The presence of persistent conductivity is explained by the high concentration of traps in the Ga2O3 film and their recharging under UV irradiation. Radiation with an energy quantum below the the β-Ga2O3 band-gap changes the charge state of trap centers in a gallium oxide film. This effect leads to an increase in photocurrent under UV exposure and increases the stability of detectors.

The paper presents a comparison of the responses of sensors to ammonia in continuous heating and thermal cycling modes, and also shows the dependence of the response time of the sensors on the content NH₃. Thin films of tin dioxide were obtained using RF magnetron sputtering, and then annealed in air at a temperature of 425°C for 24 hours. In thermal cycling, the temperature of the heating cycle remains constant 400 °C (duration of the heating cycle was 8 s). The temperature of the cooling cycle changes in the range 200 °C – 100 °C, but duration of cooling of the cooling cycle was remained constant of 5 s. It was shown that the thermal cycling mode has several advantages over the constant heating mode. The experiments showed that sensors based on SnO₂:Sb have short response times – less than 3 seconds.

The influence of operating modes on the response of ammonia sensors based on tin dioxide films has been studied. Samples have been obtained as a result of high-frequency magnetron sputtering of a SnO₂:Sb target on sapphire substrates with predeposited Pt electrodes and a heater. Varying the heating cycle duration and reducing the cooling cycle temperature may increase the response by one or two orders of magnitude. The results are explained as being due to the change in the density of chemically adsorbed oxygen on the surface of the SnO₂:Sb film depending on the temperature regime.