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The characteristics of metal-insulator-semiconductor (MIS) structures based on insulating PbSnTe:In films with compositions in the vicinity of band inversion grown by molecular-beam epitaxy (MBE) are studied. It is shown that a number of features of the films can be due to a ferroelectric phase transition with a Curie temperature in the range of about T ≈ 15–20 K.

The characteristics of MIS structures based on insulating PbSnTe:In films grown by molecular beam epitaxy (MBE) with compositions near the band inversion are studied. It is shown that a number of their features can be induced by a ferroelectric phase transition with the Curie temperature in the range of 15-20 K. The injection and detection of spin-polarized electrons in PbSnTe:In are studied by using ferromagnetic contacts Co and Co $${}_{40}$$ Fe $${}_{40}$$ B $${}_{20}$$ . A spin-valve effect is discovered by measuring the magnetoresistance in local geometry at a distance of more than 30 $$mu$$ m from ferromagnetic contacts. The presence of a surface spin-polarized state with a linear dispersion law is demonstrated by means of the photoemission with angular and spin resolution.

The dependence of the photoconductivity sign on the bias voltage, intensity, and duration of illumination is studied for PbSnTe:In films in the space-charge-limited current regime. The role of traps (including surface ones) with a complex energy spectrum in the effects under observation is discussed.

High-resistance Pb1 –xSnxTe〈In〉 layers grown by molecular beam epitaxy on BaF2(111) substrates with compositions close to band inversion have been investigated. The I–V characteristics and relaxation dependences of the photocurrent of the structures in dependence on the chemical surface treatment and subsequent exposure of the samples in air have been examined. It has been observed that the characteristics significantly transform depending on the physicochemical surface state. It has been found that the chemical surface treatment in the hydrochloric acid solution in isopropyl alcohol leads to an increase in the current by up to four orders of magnitude with the subsequent recovery of the I–V characteristics upon exposure of the samples in air for several days.

The features of transient processes under the field effect in PbSnTe:In films with a variation in the current up to a factor of 105 are studied at helium temperatures. These features qualitatively correspond to a model, in which a high concentration of traps with different parameters is present on the PbSnTe:In surface. The role of the surface is confirmed by a strong variation in the experimental characteristic after the chemical removal of native oxides from the PbSnTe:In surface and its passivation by an Al2O3 layer.

The growth temperature dependences of the capacitance–voltage characteristics and chemical stability of the CaF2/BaF2 buffer layers formed on Si by molecular beam epitaxy have been investigated. Secondary ion mass spectrometry and X-ray photoelectron spectroscopy studies of the CaF2/Si interface suggest that the observed variations can be caused by the enrichment of the Si surface layer with calcium.

This paper reports a study of the current–voltage (I–V) features of the p-i-p structures based on Pb1–xSnxTe:In films with the tin content х ≈ 0.31 in which the metal–insulator transition occurs. It is shown that the photocurrent is the hole current under light interband excitation, and electron trapping is dominant. The experimental and theoretical data are compared.

Based on the notions that PbSnTe:In is a direct-gap semiconductor, the radiative-recombination lifetime is calculated, and the photocurrent relaxation and dependences of the instantaneous electron and hole lifetime are calculated under the assumption that PbSnTe:In is a disordered structure containing capture centers. These calculations explain such experimentally observed peculiarities of PbSnTe:In as a high photosensitivity in a wide wavelength range, pinning of the Fermi level, and long-term photocurrent relaxation. Calculations are also compared with experimental data and the possible parameters of photodetectors are evaluated.

In present work, the effect of Pb1-xSnxTe (1 1 1) surface chemical treatment on electrophysical and optical properties was studied. It was shown that treatment of Pb1-xSnxTe (1 1 1) surface in HCl-isopropanol (HCl-iPA) solution led to removal of native oxides and surface enrichment by elemental tellurium of several nm thickness. Subsequent anneals in vacuum led to desorption of elemental tellurium and revealing (1x1) surface structure. We present angle resolved photoemission spectroscopy (ARPES) measurements of the surface states on chemically prepared (1 1 1) oriented MBE-grown films of Pb1-xSnxTe, a three-dimensional topological crystalline insulator (TCI). The surface states with Dirac-like dispersion at Γ in the surface Brillouin zone were detected. The dark current and photocurrent were found in strong dependence on the surface chemical procedure and composition. The relative simplicity of the preparation technique is encouraging, and suggests a clear path for future investigations of TCI states on alternative surface orientations in (Pb,Sn)Te solid solutions and applied aspects of TCI research.

A technique is described for the local indium doping of epitaxial films of a p-type PbSnTe solid solution to obtain a metal-insulator transition at liquid-helium temperatures. The indium was diffused from the surface of the film, from an In layer several nanometers thick, whereas the shape and size of the doped layer were set by a mask. It is emphasized that the oxide layer should be removed before indium deposition, and that the thickness of the deposited indium layer should be precisely chosen based on the thickness of the PbSnTe film. The results of using this technique for films having different compositions and the results of measurements performed on a planar p-i-p structure are considered.

A model of the Pb1–x Sn x Te:In compound, based on concepts of the theory of disordered systems is considered. The temperature dependences of the Fermi-level position and carrier concentration are calculated depending on the indium doping level and are compared with experimental data. The transient current–voltage characteristics are calculated in the mode of injection from the contact and current limitation by space charge at various voltage-variation rates. The data obtained are compared with the experiments. It is demonstrated that the shape of the characteristics is controlled by the parameters of electron capture at localized states. Photocurrent relaxation in a magnetic field is studied, and the mechanism of such relaxation is discussed under the assumption of the magnetic freezing of carriers.

The current-voltage characteristics (CVC) of PbSnTe:In films with a tin content of x ≈ 0.29 at helium temperatures with unipolar injection from the contacts and limitation by the space charge in a magnetic field of up to 4 T have been studied. Analysis of the CVC has shown that increasing the magnetic field from 0 to 4 T leads to changes in the CVC pattern. A relationship between these changes and the presence of a multilevel system of traps located in the band-gap zone has been suggested..

The flowing of the injection current in Pb1 − xSnxTe:In structures (x ≥ 0.3) with various metal contacts at the temperature of helium is considered. The current-voltage characteristics (CVCs) of the structures in the dark and when they are illuminated from the blackbody model are given. It is found that the CVCs depend on the materials of the metal contact. The localized state density distribution over the forbidden band in structures with various contacts is given and the influence of the contact region and localized states on the CVC is discussed. The problems of constructing photodetectors with optimum threshold characteristics are discussed.

Photoelectric properties of Pb1 − xSnxTe:In films with composition x > 0.3 in the temperature range from 4.2 to 80 K have been investigated. High sample sensitivity to black-body radiation has been discovered at the temperature of helium, and as the temperature of the radiation source decreases the sensitivity increases, which can be connected with the optical-frequency transition in the short-wavelength infrared and terahertz spectral range. The detectivity value D* = 8.2 × 1016 cm · Hz1/2/W corresponding to the NEP = 3.1 × 10−18 W/Hz1/2, has been obtained at detector temperature 4.2 K and TBBR = 15 K.