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Nanostructures with Ge–Si quantum dots for infrared photodetectors

Izhnin I. I., Fitsych O. I., Voitsekhovskii A. V., Kokhanenko A. P., Lozovoy K. A., Dirko V. V.

Opto-Electronics Review

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2018

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Vol. 26, No. 3

195--200

EN

In this paper questions of optimization of growth conditions in the method of molecular beam epitaxy for creation of high-efficient quantum dot infrared photodetectors are considered. As a model material system for theoretical investigations, heterostructures with germanium-silicon quantum dots on the silicon surface are chosen. For calculations of the dependencies of quantum dots array parameters on synthesis conditions the kinetic model of growth of differently shaped quantum dots based on the general nucleation theory is proposed. The theory is improved by taking into account the change in free energy of nucleation of an island due to the formation of additional edges of islands and due to the dependence of surface energies of facets of quantum dots on the thickness of a 2D wetting layer during the Stranski–Krastanow growth. Calculations of noise and signal characteristics of infrared photodetectors based on heterostructures with quantum dots of germanium on silicon are done. Dark current in such structures caused by thermal emission and barrier tunneling of carriers, as well as detectivity of the photodetector in the approximation of limitation by generation-recombination noises are estimated. Moreover, the presence of dispersion of quantum dots by size is taken into account in the calculations of the generation-recombination noises. Results of calculations of the properties of structures with quantum dots and their dependencies on growth parameters, as well as the characteristics of quantum dot photodetectors are presented. Comparison of the estimated parameters of quantum dots ensembles and the characteristics of quantum dot photodetectors with experimental data is carried out.

2

Ion etching of HgCdTe : properties, patterns and use as a method for defect studies

Izhnin I. I., Mynbaev K. D., Voitsekhovskii A. V., Korotaev A. G., Fitsych O. I., Pociask-Bialy M.

Opto-Electronics Review

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2017

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Vol. 25, No. 2

148--170

EN

Analysis is performed of the contemporary views on the effect of ion etching (ion-beam milling and reactive ion etching) on physical properties of HgCdTe and on the mechanisms of the processes responsible for modification of these properties under the etching. Possibilities are discussed that ion etching opens for defect studies in HgCdTe, including detecting electrically neutral tellurium nanocomplexes, determining background donor concentration in the material of various origins, and understanding the mechanism of arsenic incorporation in molecular-beam epitaxy-grown films.

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Influence of composition of the near-surface graded-gap layer on the admittance of metal-insulator-semiconductor structures based on graded-gap MBE n-Hg₁₋xCdxTe in wide temperature range

Voitsekhovskii A. V., Nesmelov S. N., Dzyadukh S. M.

Opto-Electronics Review

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2014

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Vol. 22, No. 4

236-244

EN

Influence of the CdTe content in a near-surface graded-gap layer on the admittance of MIS-structures fabricated on the basis of heteroepitaxial Hg₁₋xCdxTe (x = 0.22−0.23 and 0.31−0.32) films grown by molecular beam epitaxy was investigated in a wide temperature range. It is shown that a temperature drop from 77 K to 8 K results in a decrease of hysteresis of the capacitance-voltage (C−V) characteristics and a decrease of frequencies which corresponds to a high-frequency behaviour of C−V characteristics of MIS-structures based on n-HgCdTe (x = 0.22–0.23) with and without graded-gap layersand also for MIS-structures based on n-HgCdTe (x = 0.31–0.32). Temperature dependences of the resistance of the epitaxial film bulk and differential resistance of the space-charge region (SCR) in strong inversion mode were studied. The experimental results can be explained by the fact that for MIS-structures based on n-HgCdTe (x = 0.22–0.23) with the graded-gap layers and for MIS-structures based on n-HgCdTe (x = 0.31–0.32), the differential resistance of SCR is limited by Shockley-Read generation at 25–77 K. Differential resistance of SCR for MIS-structures based on n-HgCdTe (x = 0.22–0.23) without the graded-gap layers is limited by tunnelling through deep levels at 8–77 K.

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Influence of near-surface graded-gap layers on electrical characteristics of MIS-structures based on MBE grown HgCdTe

Voitsekhovskii A. V., Nesmelov S. N., Dzyadukh S. M., Varavin V. S., Dvoretskii S. A., Mikhailov N. N., Sidorov Y. G., Yakushev M. V.

Opto-Electronics Review

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2010

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Vol. 18, No. 3

259-262

EN

The paper examines influence of near-surface graded-gap layers on electrical characteristics of MIS-structures fabricated on heteroepitaxial Hg₁₋xCdxTe films grown by molecular beam epitaxy (MBE). Two types of insulators, i.e., two-layer SiO₂Si₃N₄ and anodic oxide films were used. As it is seen from the depth and width of the valley on the C-V characteristics, the capacitance is found to vary in a wide range, in contrast to the structures without graded-gap layers. It is shown that the graded-gap layer under MIS-structures with x = 0.22 effectively reduces the tunnelling generation via deep levels and increases a lifetime of minority carriers in the space charge region and its differential resistance. The properties of the HgCdTe-insulator interfaces are studied.

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Energy-band diagrams and capacity-voltage characteristics of CdxHg₁₋xTe : based variband structures calculated with taking into account dependence of electron affinity on a composition

Voitsekhovskii A. V., Gorn D. I., Nesmelov S. N., Kokhanenko A. P.

Opto-Electronics Review

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2010

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Vol. 18, No. 3

241-245

EN

The purpose of this scientific work is the research of energy-band diagrams and capacity-voltage characteristics of CdxHg₁₋xTe -based variband heteroepitaxial structures with taking into account the dependence of electron affinity on the composition. Numerical simulations of energy-band diagrams and capacity-voltage characteristics for metal-insulator-semiconductor structures based on CdxHg₁₋xTe -variable composition layers are carried out in this work. Energy diagrams are calculated with taking into account the dependence of electron affinity on the composition x of CdxHg₁₋xTe. This dependence was obtained in terms of dependence of the local electroneutrality level on the composition for CdxHg₁₋xTe.

6

Capacitance-voltage characteristics of MIS-structures on the basis of graded-band MBE Hg₁₋xCdxTe at passivation by epitaxially grown in situ CdTe

Voitsekhovskii A. V., Nesmelov S. N., Dzyadukh S. M., Varavin V. S., Dvoretskii S. A., Mikhailov N. N., Sidorov Y. G., Yakushev M. V.

Opto-Electronics Review

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2010

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Vol. 18, No. 3

263-266

EN

The electrical properties of the interface between Hg₁₋xCdxTe (x = 0.22 and x = 0.32-0.36) and CdTe prepared in situ molecular beam epitaxy were estimated at 77 K. The methods of determination of main parameters of interface semiconductor/insulator and insulator from capacitance-voltage characteristics of MIS-structures based on graded-band Hg₁₋xCxTe have been developed. The fixed charge states density, fast surface states density, and density of mobile charge are obtained from capacitance-voltage measurements. For improvement in stable and electrical strength of insulator coating for several samples over CdTe additional protective layers SiO₂-Si₃N₄ are formed for x = 0.22 and ZnTe for x = 0.32-0.36.

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Conductivity anisotropy of CdHgTe MBE layers with a periodic surface microrelief

Voitsekhovskii A. V., Kokhanenko A. P., Nesterovich N. V., Varavin V. S., Dvoretsky S. A., Sidorov Y. G., Mikhalov N. N.

Opto-Electronics Review

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2003

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Vol. 11, No. 2

151-154

EN

The surface microrelief of CdHgTe layers grown by molecular beam epitaxy (MBE) method has been studied by means of atomicforce microscopy. A periodic surface microrelief in the form of an ordered system of extended waves with the characteristic period 0.1-0.2 um has been detected on epilayers grown at increased temperatures. Angular dependencies of the conductivity at 77 K have been measured and the conductivity anisotropy has been detected with a minimum in the direction transverse to microrelief waves. A feature of the transmission spectrum and the spectrum change after film annealing are observed. It is assumed that walls growing in the direction from the substrate to the surface are formed under microrelief wave slopes. Such structure can cause the observed feature of the transmission spectrum if the adjacent walls have different composition. In this work a calculation of spectral characteristics taking into account the influence of variable gap composition and nonuniformity of the composition through the depth has been carried out.