S. I. Drapak

Native oxide emerging of the cleavage surface of gallium selenide due to prolonged storage

The crystal structure and surface morphology of native oxide emerging on the surface of the (0001) cleavage of undoped and Cd-doped or Dy-doped single crystals of layered GaSe due to prolonged storage in air are studied. The factors that lead to the differences in the outward appearance of oxide films on the surface of undoped (dull surface) and doped samples (transparent films) are analyzed. The results of studies of electrical properties of the 〈gallium selenide〉-〈native oxide〉 systems are reported. It is shown that the films of native oxide on the GaSe surface feature current instability with an N-like current-voltage characteristic. Attention is paid to low values of effective permittivity of native oxide.

Variation in the built-in potential of a photodiode based on an n-InSe-p-GaSe heterojunction in the course of aging

Variations in the built-in potential of optical contact between n-InSe and p-GaSe in the course of long-term (over 10 years) storage under normal ambient conditions were investigated in the case of n-InSe-p-GaSe heterostructures. It was found that the above potential increases considerably with time. This increase is accounted for by the fact that the surfaces of InSe and GaSe become closer to each other as a result of the diffusive spread of oxygen originally adsorbed at the interface into the bulk of the contacting semiconductors. As a result, InSe/GaSe islands are formed and shunt the structure (regions of real close InSe/GaSe contact are formed).

On the mechanisms of current transfer in n-In2Se3-p-GaSe heterostructures

The current-voltage and capacitance-voltage characteristics of originally fabricated photosensitive, radiation-stable anisotype n-In2Se3-p-GaSe heterostructures are presented. The electrical properties of these heterostructures depend on the method of fabrication, which is explained by variation of the band parameters of indium selenide.

X-ray diffraction study of the molecular propolis films deposited from an alcohol solution onto the cleavage surfaces of layered V2VI3 compounds

The structures of the molecular propolis films deposited from an alcohol solution on the (0001) cleavage surface of layered bismuth selenide and telluride are studied by X-ray diffraction. Despite the chemical interaction between the semiconductor substrates and the organic-substance components, the molecular structural ordering of the propolis films is shown to be identical to that in the films of this substance on the surface of amorphous glass substrates. The chemical and deformation interaction between the organic substance and the layered V2VI3 compounds is found to result in the formation of an organic-inorganic sandwich nanostructure at a distance of ∼0.3 μm from the layered crystal-propolis film interface.

Effect of the buffer layer of GaSe intrinsic oxide with nanometer thickness on electrical, photoelectric, and emissive properties of ITO-GaSe heterostructures

The effect of the thickness of a buffer layer of intrinsic GaSe oxide on the electrical, photoelectric, and emissive properties of ITO-GaSe heterojunctions is studied. It is established that the introduction of a Ga2O3 layer with thickness as large as 5–6 nm into the ITO-GaSe heterojunction results in a change in the current-flow mechanisms in the structure, an increase in the open-circuit voltage Voc by more than twofold (in this case, the situation where the Voc exceeds appreciably the contact potential difference is realized), an increase in the electroluminescence intensity by more than an order of magnitude, and an increase in the efficiency of photoconversion by more than two times compared to samples where the Ga2O3 layer was not grown intentionally.

The effect of photocurrent amplification in an In2O3-GaSe heterostructure

The effect of photocurrent amplification in an In2O3-GaSe heterostructure with the barrier plane perpendicular to the base semiconductor layer was experimentally observed. At a reverse bias of U=10 V, the gain reached M≈82 and the absolute current sensitivity amounted to 30–32 A/W. An analysis of the current-voltage characteristics allowed a mechanism of the charge transfer through dielectric to be determined that is always operative on the surface of gallium monoselenide in the heterostructures fabricated by spraying. It is suggested that the mechanism of conductivity can be modified by changing the barrier plane orientation from parallel to perpendicular to the GaSe layers.

Experimental investigation of effect of aromatic hydrocarbons on resistivity of indium selenide

The regular features in the variation of resistivity of n-and p-type indium selenide in the direction parallel to the hexagonal symmetry axis of crystals during its intercalation with aromatic-hydrocarbon molecules (benzene and naphthalene) are investigated. For the first time, the possibility of decreasing the resistivity of n-InSe aged under pressure of C10H8 saturated vapors to values comparable to those in semiconductors used for manufacturing high-performance solar cells (for example, Si) is found. The qualitative model explaining the transition of n-type indium monoselenide from a “high-resistance” to “low-resistance” state during its intercalation with naphthalene molecules is proposed.

Asymmetric current transfer in isotype n-In2Se3/n-InSe heterocontacts

We have studied the mechanisms of current transfer and the capacitance-voltage characteristics of a radiation-resistant isotype n-In2Se3/n-InSe heterocontact in which the region depleted of major charge carriers is localized predominantly in a relatively low-ohmic semiconductor—the α-type In2Se3 with a large density of defects. The spectrum of the relative quantum efficiency of photoconversion in this structure depends on the thickness of the In2Se3 layer and on the geometry of illumination of the heterocontact.

Effect of uniaxial compression on the photoconversion parameters in a p-GaSe-n-InSe optical contact

The effect of uniaxial pressure in the direction perpendicular to the localization plane of the interface for n-InSe-p-GaSe heterojunctions on a variation in the saturation photovoltage and short-circuit current is studied. It is shown that, in InSe/GaSe optical contacts subjected to a pressure P = 35–40 kPa, the open-circuit voltage increases almost twofold and the short-circuit current increases by more than a factor of 5 as compared to the values observed in the initial samples, which makes it possible to expect that the efficiency of photoconversion can be increased to 15–16% in the structures under consideration.

Energy band diagram of a photosensitive Sn-p-InSe structure

Photosensitive Sn-p-InSe structures obtained by thermal deposition of Sn in vacuum onto thermally pretreated p-InSe substrates are well described within the framework of a MIS model with the insulating layer represented by a film of wide-bandgap γ-In2Se3 with Eg=2.0 eV formed as a result of thermal treatment of the base semiconductor.