T. N. Ushakova

Photosensitive structures based on ZnP2 single crystals of monoclinic and tetragonal modifications: Fabrication and properties

The method of gas-phase resublimation is used to grow the single-crystals of monoclinic and tetragonal modifications whose composition are identical and corresponds to the ZnP2 stoichiometry. The crystal-lattice parameters are determined and natural facets of the crystals of both modifications are identified. The obtained single crystals were used to fabricate for the first time the Schottky barriers and welded point structures; the latter exhibited rectification and the photovoltaic effect. On the basis of the first studies of photosensitivity of obtained structures subjected to the natural and linearly polarized radiation, the character of interband transitions is suggested, the values of the band gap are determined, and the influence of the position ordering of atoms on the structures’ properties is observed. The phenomenon of natural photopleochroism observed in the structures based on oriented ZnP2 single crystals were studied. It is concluded that it is possible to use the zinc diphosphide in photoconversion of the intensity and polarization of optical radiation.

Electronic properties of ZnGeP2 crystals obtained by a solid-phase reaction

The low-temperature synthesis of ZnGeP2 by a solid-phase reaction is carried out for the first time, and photosensitive heterostructures based on it are obtained. The spectral dependences of the photoluminescence of the crystals and the photoconversion quantum efficiency of the heterostructures are investigated. Conclusions regarding the prospects of the new technology for improving the optical quality of ZnGeP2 are drawn.

Creation and studies of the photosensitivity of Ox/n-GaP structures

Photosensitive heterostructures Ox/n-GaP, where Ox is a native oxide, are created for the first time by thermal interaction of a GaP crystal with ambient air. The photovoltaic effect of the heterostructures, which dominates upon illumination of the structure’s oxide film, is revealed. First, the spectral dependences of the relative quantum efficiency of photoconversion for the obtained heterostructures are analyzed, the character of the band-to-band transitions is determined, and the GaP band gap is estimated. A conclusion is drawn regarding the potential of using the vacuum-free thermal oxidation of homogeneous n-GaP single crystals in ambient air to fabricate broadband photoconverters of optical radiation.

Photosensitive Ox/GaAs heterojunctions: Creation and properties

A method for the thermal oxidation of GaAs crystals in air is suggested and the first photosensitive Ox/n-GaAs heterojunctions, where Ox is a native oxide, are fabricated. The steady current-voltage characteristics and spectra of relative quantum efficiency of the new structures are studied. The features of the spectra of photoactive absorption of the obtained heterojunctions are discussed. The potential of using vacuumfree thermal oxidation of the GaAs crystals in air to fabricate broadband heterophotoconverters of optical radiation on their basis is established.

Photoelectrochemical cells based on In2S3 single crystals

The single crystals of tetragonal modification t-In2S3 are grown by the planar crystallization of the melt. On their basis, the photosensitive H2O/t-In2S3 cells are fabricated, and the spectra of their quantum efficiency are investigated. The broadband photosensivity of H2O/t-In2S3 cells is determined. On the basis of the photosensivity spectra, the character of interband transitions and the t-In2S3 band gaps corresponding to them are determined. The possibility of using the t-In2S3 crystals in broadband photoconverters of natural and polarized radiations is shown. The relation between the energy spectrum and the phase state of In2S3 crystals is revealed.

Physical properties of CdGeAs2 crystals grown by solid-state synthesis

The authors of this paper offer experimental proof that the method of solid-state reactions can be used to make ternary II–IV–V semiconductors (using CdGeAs2, for example). In this method, the semiconductor group-IV component reacts with a vapor phase containing the group-II and group-V components of the compound. Initial results of studies of the physical properties of CdGeAs2 crystals grown in this way and photosensitive heterostructures made from these crystals indicate that this new growth technology promises to improve the quality of II–IV–V semiconductors, thereby enabling novel practical applications of these materials.

p-GaSb(Ox)/n-GaSb native-oxide heterojunctions: Non-vacuum process and photoelectric properties

A new non-vacuum technology is proposed and anisotype photosensitive heterojunctions (native oxide of a narrow-gap III–V semiconductor)-(binary compound) p-GaSb(Ox)/n-GaSb are fabricated for the first time. The developed technological process is based on the surface thermal interaction of a GaSb crystal with components of the normal Earth atmosphere. Based on original physical-technological studies of interaction in the GaSb/(air medium) system, it is found that p-GaSb(Ox) native-oxide films obtained in such a way exhibit high adhesion to the surface of the initial gallium antimonide n-GaSb. The steady-state current-voltage characteristics and spectral dependences of the relative photoconversion quantum efficiency of the obtained p-GaSb(Ox)/n-GaSb heterojunctions are first measured. On this basis, the systematic features of charge transport and photosensitivity are discussed. A new possible application of the non-vacuum thermal oxidation of GaSb films in the development of optical radiation photodetectors on substrates of homogeneous gallium antimonide n-GaSb crystals is first detected and implemented.

Creation and photoelectric properties of Ox/p-InAs heterostructures

For the first time, heterostructures represented by the contact of a thin film of indium-arsenide intrinsic oxide Ox with an InAs wafer are obtained by the surface thermal interaction of indium arsenide with the normal Earth air atmosphere. The first I–V characteristics and spectral dependences of the photosensetivity of Ox/p-InAs heterostructures are investigated. For the first time, the rectification is revealed for these heterostructures, and the spectral dependences of the photosensivity are analyzed. A conclusion concerning the possibility of using the new technology for fabricating broadband optical Ox/p-InAs-based photodetectors is advanced.

Photoelectrochemical cells based on ternary compounds CuIn2n + 1Se3n + 2 (n = 3-6)

Single crystals of ternary CuIn2n + 1Se3n + 2 semiconductors with the composition index n = 3, 5, 6 were grown for the first time using the direct crystallization method. It was shown that these crystals have hexagonal symmetry and close unit cell parameters. Photoelectrochemical cells based on CuIn2n + 1Se3n + 2 and In2Se3 single crystals were fabricated. Their photosensitivity spectra were measured for the first time, which were used to determine the nature of interband transitions and the band gap. The weak dependence of the parameters of the band’s spectrum and unit cell of these semiconductors at n ≥ 2 was attributed to the features of the interatomic interaction in such phases. It was concluded that new CuIn2n + 1Se3n + 2 semiconductors can be used in broadband photoconverters of optical radiations.

Photosensitivity of heterostructures based on finely ground semiconductor phases

A new type of heterostructure is suggested and developed. The heterostructures are based on the direct contact of a bulk semiconductor with a dielectric layer in which a finely ground semiconductor phase is dispersed. In Si-and GaAs-based heterostructures of this type, rectification and photovoltaic effects are observed. It is shown that illumination of such structures so that the side of the dielectric layer with the built-in finely ground semiconductor phase is exposed to light induces a broadband photovoltaic effect deep within the fundamental absorption band of the bulk semiconductor.