I. K. Polushina

Physical properties of CuxAg1−xIn5S8 single crystals and related surface-barrier structures

The electrical properties and photoluminescence spectra of single crystals of the ternary compounds CuIn5S8, AgIn5S8 and their solid solutions have been investigated. We have determined the type of conductivity, the mobility, charge carrier concentrations and energies of the radiative transitions in these materials. We have fabricated surface-barrier structures from these single crystals and measured the voltaic photosensitivity.

Photoelectric phenomena in ZnO:Al-p-Si heterostructures

Al-doped zinc-oxide (ZnO:Al) films are obtained by magnetron sputtering. Based on an investigation of electrical properties of the films, it is shown that the electron density in these films is as high as 5×1020 cm−3 and is practically constant in the temperature range 77–300 K, which indicates high efficiency of doping ZnO with an Al impurity. It is found that the deposition of thin films (d≈1 µm) on the p-Si(111) surface leads to the formation of heterostructures with the highest photosensitivity of ∼400 V/W at T=300 K, which oscillates in the spectral range 1.3–3.5 eV. With the oblique incidence of linearly polarized radiation, induced pleochroism emerges in such heterostructures. The magnitude of pleochroism oscillates in the range 5–40% (θ≈75°), which is associated with the interference phenomena in the ZnO films. The prospects of using the heterostructures obtained as highly selective photosensors of natural and linearly polarized radiation are considered.

Photosensitive structures based on CdGa2Se4 single crystals

Photosensitive structures based on CdGa2Se4 single crystals have been fabricated for the first time: In/CdGa2Se4 surface-barrier structures and InSe/CdGa2Se4 heterostructures. The current-voltage characteristics and the quantum efficiency spectra of these structures were studied. The polarization photosensitivity of In/CdGa2Se4 structures were found. The photosensitivity is discussed taking into account the photoactive absorption in CdGa2Se4 crystals in the impurity-related and intrinsic spectral ranges. A conclusion has been made that CdGa2Se4 single crystals are promising for commercial applications in photoelectric converters of unpolarized and linearly polarized light.

Optoelectronic effects in p-CdGeAs2 single crystals and structures based on them

Spectra of inelastic light scattering by optical phonons in p-CdGeAs2 single crystals were obtained for the first time. The observed clear polarization dependence and the absence of any appreciable dependence of the intensity and frequency of the observed lines when the sample is swept in ≈300 µm steps indicates these CdGeAs2 single crystals grown by directional crystallization from a near-stoichiometric flux, are of high quality and homogeneous. The type of symmetry of the observed phonon lines is interpreted and it is shown that the force constants in CdGeAs2 and CdSnP2 crystals differ slightly. Temperature dependences of the electrical conductivity and the Hall constant were studied in oriented homogeneous p-CdGeAs2 single crystals. It was established that the conductivity of these crystals is determined by the deep acceptor level EA=0.175 eV and has the degree of compensation 0.5–0.6. The temperature dependence of the Hall mobility reflects the competition between impurity and lattice mechanisms of hole scattering. The photosensitivity of In/CdGeAs2 surface barrier structures reaches 20 µA/W at T=300 K and remains at this level within the fundamental absorption of CdGeAs2. It is concluded that these structures may be used as wide-band photoconverters for natural light and as selective photoanalyzers for linearly polarized radiation.

Photovoltaic effects in CdV2S4 single crystals and structures based on them

Single crystals of the CdV2S4 ternary compound are grown, and their crystal structure, electrical properties, and optical absorption are studied. The substitution of vanadium for Group III element in AIIB2III C4VI compounds results in the formation of crystals of n-type conduction with an electron density of ∼1018 cm−3 and a Hall mobility Un≈150 cm2/(V s) at T=300 K, which is limited by scattering on lattice vibrations. Rectifying photosensitive structures based on CdV2S4 single crystals are fabricated for the first time, their photoelectric properties are studied, and a conclusion is made on their applicability in the design of wide-spectral-range photodetectors of unpolarized light.

Fabrication and properties of ZnFe2S4 single crystals and structures based on them

A new class of ternary semiconductor compounds has been proposed and synthesized. ZnFe2S4 single crystals, which belong to this class, have been grown for the first time; and their structural, electrical, and optical properties have been investigated. The first photosensitive structures have been fabricated, and their photoelectric characteristics have been studied. A conclusion was made that heterostructures and surface-barrier structures based on ZnFe2S4 single crystals are promising for practical applications.

Electric and luminescence properties of GaAs-AIIBIVC 2 V single crystals

GaAs-AIIBIVC2V single crystals are grown by crystallization from dilute gallium fluxed solutions. The electric and luminescence properties of the crystals obtained are investigated. It is shown that the technological process is accompanied by the standard doping of gallium arsenide and makes it possible to grow gallium arsenide single crystals whose optoelectronic properties are controlled by the AIIBIVAs2 compound introduced into the fluxed solution.

Physical properties of n-CdGeAs2 single crystals prepared by low-temperature crystallization

The first results obtained in studies of the temperature dependences of electrical conductivity and Hall constant of n-CdGeAs2 single crystals prepared by low-temperature crystallization are reported. It has been established that the method developed permits growing single crystals with a free-electron concentration ⋍(1−2)×1018 cm−3 and a Hall mobility ⋍10000 cm2/(Vs) at T=300 K. It is shown that the temperature dependence of Hall mobility exhibits a behavior characteristic of electron scattering by lattice vibrations, whereas below 150 K a deviation from this law is observed to occur evidencing an increasing contribution of static lattice defects to scattering. The Hall mobility in the crystals prepared was found to reach ⋍36000 cm2/(Vs) at 77 K. Photosensitive heterojunctions based on n-CdGeAs2 single crystals were prepared. The spectral response of the photosensitivity of these structures is analyzed. It is concluded that this method is promising for preparation of perfect CdGeAs2 crystals.