Vasilij Semenovich Varavin

Subject of study. Epitaxial films of Hg_0.7Cd_0.3Te solid solutions grown by molecular beam epitaxy and doped with arsenic to obtain hole-type conductivity in order to form p-n junctions for the production of infrared photodetector structures are studied. Aim of study. The types and characteristics of defects formed during arsenic doping of epitaxial films of Hg_0.7Cd_0.3Te solid solutions grown by molecular beam epitaxy and the effect of doping on the level of disorder in the solid solution are determined. Method. Ellipsometry, optical transmittance, photoluminescence, and photoreflectance are used. Main results. The initial material is shown to have high quality in terms of film bulk and surface quality, and the quality was found to improve after two-stage activation thermal annealing. Annealing has been shown to activate the arsenic with the formation of shallow (7–8 meV) acceptor levels. No side defects were found to occur as a result of the introduction of arsenic into the films during growth and annealing. Practical significance. This research demonstrated the effectiveness of doping epitaxial films of Hg_0.7Cd_0.3Te solid solutions with arsenic as an acceptor impurity in order to produce layers with hole conductivity during the production of photodiode structures.

The subject of study is barrier nBn structures based on (013)CdxHg_1−x Te/CdTe/ZnTe/GaAs solid solutions. The purpose of the work is the creation of barrier nBn structures based on Cd_xHg_1−x Te solid solutions with a given composition distribution profile and doping level intended for the manufacture of highly sensitive infrared photodetectors in the spectral range of 3–5 µm operating at elevated temperatures. Method. The growth of barrier nBn HgCdTe structures is carried out by molecular beam epitaxy on (013)GaAs substrates with ZnTe and CdTe buffer layers and control of the thickness and composition of the layers in real time by a high-speed ellipsometric method. Doping of the layers during the growth process to the required level is carried out with indium from a Knudsen-type effusion source with precision control of its temperature (flow). The composition and thickness of the layers are determined during the growth process from in-situ measurements of ellipsometric parameters and transmission and reflectance spectra with sequential etching of the ex-situ layers. The concentration of the majority charge carriers in the grown structures is determined from Hall measurements by the Van Der Pauw method using layer-by-layer etching. Main results. Barrier nBn structures based on HgCdTe are obtained. The parameters of the composition and thickness of the layers are 0.3–0.35, 0.6–0.8, and 0.31–0.36 mole fractions and 3–4, 0.2–0.35, and 1–1.3 µm for the absorbing, barrier, and contact layers, respectively. The concentration of the majority carriers is (0.6−3)×10¹⁶, (0.6−3)×10¹⁶, and (0.9−5)×10¹⁷cm⁻³ for the absorbing, barrier, and contact layers, respectively. A good correlation between the distribution profile of the composition and the doping level throughout the thickness of the grown structure, which is specified during the growth process with the results of subsequent post-growth measurements, is shown. Practical significance. The results of growing and characterizing the nBn structure obtained in this work are intended for the development of infrared photodetectors for the size, weight, and power (SWaP) technology, with high sensitivity in the spectral range of 3–5 µm, various formats, and operating at elevated temperatures, for infrared optoelectronic and thermal imaging devices.

The subject of the study is epitaxial films of Hg_1−x Cd_xTe solid solutions with the mole fraction of CdTe, x, varying from 0.3 to 0.7, grown by molecular beam epitaxy, and intended for the manufacture of photodetecting and laser structures operating in the infrared range. The aim of the study is to determine the relationship between the optical and microscopic properties of Hg_1−x Cd_xTe solid solutions with fluctuations in their composition. The methods include optical transmission, photoluminescence, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Main results. By comparing the results of optical, structural, and microscopic studies, it is shown that, for the films with x≈0.3, the research data on optical properties make it possible to adequately estimate the bandgap and determine the chemical composition of the material. The high perfection of this material is shown, and it is confirmed that its disorder is caused only by the specifics of the formation of semiconductor solid solutions. For the films with x≈0.7, it is established that data on the bandgap and composition can only be obtained from ellipsometric studies and measurements of optical transmission, whereas photoluminescence spectra at temperatures up to room temperature are formed by optical transitions involving carriers localized on large-scale composition fluctuations. In the films with x≈0.7, the presence of uncontrolled acceptor states is also detected, which may indicate the need to optimize the technology of this material. Practical significance. The limits of applicability of photoluminescence studies for characterizing the properties of solid solutions are identified. The need for further optimization of the technology of materials with large (x≈0.7) compositions is shown.

Water --- a source electrically active centres in CdHgTe

Вода --- источник электрически активных центров в CdHgTe

The admittance of MIS structures based on n(p)-Hg_1–xCd_xTe (x = 0.21–0.23) grown by molecular-beam epitaxy on Si and GaAs substrates is studied. The possibility of increasing the value of the product of the differential resistance of the space charge region and area of the field electrode R_SCRA by creating near-surface graded-gap layers with an increased content of CdTe is investigated. It has been established that the creation of a graded-gap layer leads to an increase in the value of R_SCRA by a factor of 10–200 for MIS structures based on n-Hg_0.78Cd_0.22Te due to suppression of tunneling generation through deep levels and a decrease in the Shockley–Read current. MIS structures based on n-Hg_0.78Cd_0.22Te without a graded-gap layer grown on GaAs substrates have R_SCRA values that exceed 10 or more times the values of the same parameter for structures grown on Si substrates.