V. M. Kalygina

Ga 2 O 3 Films Formed by Electrochemical Oxidation

The effect of oxygen plasma on gallium oxide films formed by electrochemical oxidation of n-GaAs wafers with a donor concentration Nd = (1–2) × 1016 cm−3 has been investigated. It is shown that the treatment in an oxygen plasma at a temperature of 50–90°C increases the concentration of β-phase crystallites, which causes an increase in the permittivity, a decrease in the dielectric dissipation factor, and a change in the conductivity of GaAs-〈gallium oxide〉-metal structures.

Effect of thermal annealing and exposure to oxygen plasma on the properties of TiO2-Si structures

The effect of thermal annealing and exposure to oxygen plasma on the phase composition, structure, and microprofile of titanium-dioxide films deposited by high-frequency magnetron sputtering on silicon substrates is studied. The influence exerted by processing modes on the capacitance-voltage and conductance-voltage characteristics of Me-TiO2-Si-Me structures and on the density of surface states at the semiconductor-insulator interface is examined. It is shown that TiO2 films are amorphous upon their fabrication. Upon the annealing of films at 500°C in an argon atmosphere, crystallites of anatase and rutile appear in the amorphous matrix. The treatment of a titanium-dioxide film in oxygen plasma gives rise to rutile crystallites with new crystallographic planes. As a result of annealing at 750°C, the anatase phase disappears and the film becomes polycrystalline, containing only rutile crystallites. The capacitance of Me-TiO2-Si-Me structures in the accumulation mode reaches the maximum value upon annealing at 750°C, which is due to the transformation of titanium dioxide to the rutile phase. The specific capacitance is 5.9 × 10−2 F/cm3. The decrease in the capacitance of the structures and in the amount of fixed charge in the insulator upon exposure to oxygen plasma is due to the diffusion of oxygen atoms across the titanium-dioxide layer to give a SiO2 film at the TiO2-Si interface. As a result of the annealing and treatment of a titanium-dioxide film in oxygen plasma, the energy density of surface states decreases by more than an order of magnitude as compared with the unannealed samples.

Effect of oxygen plasma on the properties of tantalum oxide films

The effect of oxygen plasma on the leakage current, permittivity, and the dielectric loss tangent of Ta2O5 thin layers (300–400 nm) is studied. It is suggested to treat tantalum oxide films in oxygen plasma to control their electrical and dielectric characteristics.

Gallium-oxide films obtained by thermal evaporation

The current-voltage (I–V), capacitance-voltage (C–V), and conductance-voltage (G–V) characteristics of metal/GaxOy/GaAs/metal structures are investigated. Gallium-oxide films with a thickness of 150–170 nm are deposited by the thermal evaporation of Ga2O3 powder onto n-type GaAs substrates with the donor concentration Nd = 2 × 1016 cm−3. Treatment of the GaxOy films in oxygen plasma causes a decrease in both the forward and reverse currents and a shift of the C–V and G–V curves to higher positive voltages. The Fermi level at the insulator/semiconductor interface in the structures under study is unpinned. The density of states at the GaxOy/GaAs interface is Nt = (2–6) × 1012 eV−1 cm−2.

Mechanism of formation of the response of a hydrogen gas sensor based on a silicon MOS diode

AbstractExperimental data on the dependence of the flat-band voltage and relaxation time for the capacitance of the space-charge region in an MOS diode (Pd-SiO2-n-Si) on the hydrogen concentration in a hydrogen/air gaseous mixture are discussed. It is assumed that variation in the flat-band voltage Ufb in an MOS structure with the thickness d = 369 nm subjected to a hydrogen/air gaseous mixture can be accounted for by the formation of dipoles in the Pd-SiO2 gap due to polarization of hydrogen atoms (Ha). An analytical expression describing the dependence of variation in the flat-band voltage ΔUfb on the hydrogen concentration

Properties of TiO2 films on silicon substrate

n_{H_2 }

Solid-state image converters on the basis of the GaAs/ZnS structures

was derived. In MOS structures with d ≤ 4 nm (or MOS diodes), the value of ΔUfb is mainly controlled by passivation of the centers responsible for the presence of the surface acceptor-type centers at the SiO2-n-Si interface by hydrogen atoms. Analytical expressions describing the dependences of ΔUfb and the capacitance relaxation time in the space-charge region on