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Precision seeders (PSs) that ensure precise single-seed sowing are used both in domestic and international agricultural practices. A distinct feature of most foreign and domestic PSs designed for intertilled crops is the presence of optional equipment used to apply fertilizers simultaneously with sowing. Today, the seedbed (starter) fertilization option is a mandatory functional (consumer) characteristic of all newly developed and implemented PSs for row crops. Modern precision seeders can ensure nearly any seeding rate in the required geometric combinations (parameters) with the optimal placement (layout) of seeds in the field. One of the ways to enhance the yield of row crops is to increase the number of plants per unit area through the optimization of the seed placement (layout). The functionality of modern PSs and the introduction of new machinery systems make it possible to perform sowing with narrow row spacing and twin rows. The existing technical and technological local-band fertilization scheme implemented by modern PSs involves the continuous (uninterrupted) application of fertilizers. This results in an excessive consumption of fertilizers, and the applied nutrients are used by weeds developing in intervals between seeds. The conducted studies made it possible to optimize the row-crop sowing process with simultaneous seedbed (starter) fertilization by applying fertilizers in accordance with the 5 × 5 × 5 scheme (5 cm deeper than seeds, 5 cm away from plant rows, and in 5-cm "foci"). The 5 × 5 × 5 scheme reduces the application rate and increases the economy of fertilizers by two times and more. The proposed scheme is implemented in a technical concept codenamed "seeder for precision sowing of intertilled crops and local differentiated fertilization" (Patent of the Russian Federation no. 199944 of September 29, 2020). Its sowing unit is integrated with the dosing device for seedbed (starter) fertilizers. [ABSTRACT FROM AUTHOR]

Excitonic quality CuInSe2 crystals were studied using low-temperature (10 K) photoluminescence (PL) excited by continuous wave and nanosecond pulsed lasers at power densities from 0.01 to 76 kW/cm2. Increasing the excitation power density level to 26 kW/cm2 resulted in the appearance of a stimulated emission SE-band in the PL spectra at 1.035 eV. Further increase in the excitation level to 39 kW/cm2 generated on the top of the SE band, a structure of equidistant sharp lines attributed to laser emission. [ABSTRACT FROM AUTHOR]

Two types of long-wave infrared nBn-structures based on mercury cadmium telluride grown by molecular beam epitaxy on GaAs (013) substrates have been fabricated. For each type of device, the side walls of the mesa structures were passivated with an Al2O3 insulating film or left without passivation. The CdTe content in the absorbing layers was 0.20 and 0.21, and in the barrier layers, it was 0.61 and 0.63. The dark currents of the manufactured devices were studied in a wide range of voltages and temperatures. The values of the surface leakage component are found under various conditions. It has been shown that the surface leakage current density decreases upon passivation with an Al2O3 film. It was found that in the fabricated nBn-structures at room temperature, the surface leakage component dominates at reverse biases, and at forward biases, the dark current is determined by the combined effect of the surface leakage component and the bulk current component. From the Arrhenius plots, the values of the activation energies of the surface leakage current component were found, which are in the range from 0.05 to 0.10 eV at small reverse biases. At small reverse biases, upon cooling the samples, the role of the bulk component of the dark current increases, which at 180 K is approximately 0.81 A/cm2. In the temperature range 200–300 K, the values of the dark current density exceed the values calculated according to the empirical Rule07 model by a factor of 10-100, which indicates the possibility of creating the long-wave infrared barrier detectors by decreasing the values of the surface leakage component. [ABSTRACT FROM AUTHOR]

The admittance of test MIS structures based on nBn systems from Hg1 –xCdxTe grown by molecular beam epitaxy is investigated. Composition x in the absorbing and contact layers is 0.29; in the barrier layer, it is 0.60. An equivalent circuit of an MIS-structure based on an nBn system is proposed and the nominal values of the elements of this circuit are found under various conditions. Comparison of the temperature dependence of the barrier resistance with the Rule07 model indicates the possibility of creating efficient nBn detectors based on HgCdTe grown by molecular beam epitaxy for the 3- to 5-μm spectral range. [ABSTRACT FROM AUTHOR]

The problem of in situ temperature control during the growth of epitaxial layers of HgCdTe by molecular beam epitaxy is considered. Various approaches to solving the problem using spectroscopic ellipsometry are proposed. They are based on the temperature dependence of the optical constants spectra of the CdTe buffer layer and the growing HgCdTe layer. The results of experimental testing of these methods are presented, which show that the temperature measurement accuracy is several degrees, and the sensitivity reaches fractions of a degree. At the stage of stationary growth, it is possible to determine the change not only in the temperature, but also in the composition of the growing layer from the ellipsometric spectra. [ABSTRACT FROM AUTHOR]

High-quality single crystals of CuInSe2 with near-stoichiometric elemental compositions were irradiated with 6 MeV electrons, at doses from 1015 to 3 × 1018 cm-2, and studied using photoluminescence (PL) at temperatures from 4.2 to 300 K. Before irradiation, the photoluminescence spectra reveal a number of sharp and well resolved lines associated with free- and bound-excitons. The spectra also show broader bands relating to free-to-bound transitions and their phonon replicas in the lower energy region below 1.0 eV. The irradiation with 6 MeV electrons reduces the intensity of the free- and the majority of the bound-exciton peaks. Such a reduction can be seen for doses above 1016 cm-2. The irradiation induces new PL lines at 1.0215 eV and 0.9909 eV and also enhances the intensity of the lines at 1.0325 and 1.0102 eV present in the photoluminescence spectra before the irradiation. Two broad bands at 0.902 and 0.972 eV, respectively, are tentatively associated with two acceptor-type defects: namely, interstitial selenium (Sei) and copper on indium site (CuIn). After irradiation, these become more intense suggesting an increase in the concentration of these defects due to irradiation. [ABSTRACT FROM AUTHOR]

Mid-wave infrared nBn structures based on HgCdTe grown by molecular beam epitaxy on GaAs (013) substrates were fabricated. The composition in the absorbing layer was 0.29, and in the barrier layer it was 0.67. It was shown that the dark currents of the created nBn structures are limited by the surface leakage component. To study the bulk component of the dark current, it was proposed to use the admittance measurements of test metal-insulator-semiconductor (MIS) devices based on fabricated nBn structures in the case of the formation of a backward contact to the absorbing layer. It was established that surface leakage does not affect the dynamic resistance of the MIS device barrier. The dependence of the dynamic resistance of the barrier layer (Rb) of the MIS device in the accumulation mode on the area of the front electrode (A), voltage, and temperature was determined. It was shown that, with the exclusion of surface leakage, the values of the RbA product in a temperature range of 230–300 K at forward biases are determined by the diffusion current of holes from the contact layer, and at reverse biases, by the diffusion current from the absorbing layer. It was found that at temperatures of 210–300 K, RbA values exceeding the values of this parameter determined according to the empirical model Rule 07 were realized in the fabricated structures. [ABSTRACT FROM AUTHOR]

Accumulation of arsenic implantation-induced donor defects in heteroepitaxial Hg1−xCdxTe structures with the composition of the active layer xa = 0.30 was studied with the use of the Hall-effect measurements and mobility spectrum analysis. The studies allowed for identifying the carriers in the implantation-damaged n+-layer, namely, electrons with low and intermediate mobility, and for establishing the dependence of their concentration on the ion fluence. The electrically active implantation-induced defects in the studied structures, similar to the case of those with xa = 0.22, were identified as atoms of interstitial mercury captured by dislocation loops and quasi-point defects. In the material with xa = 0.30, a weak dependence of the concentration of low-mobility electrons on the fluence was observed. In general, a substantial difference in the properties of p+–n junctions formed as a result of arsenic implantation in the structures with xa = 0.30 and xa = 0.22 was established. The difference was explained by the effect of the graded-gap surface layer on the diffusion of charged defects released during the implantation. [ABSTRACT FROM AUTHOR]