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MBE-grown MCT hetero- and nanostructures for IR and THz detectors

Dvoretsky S. A., Mikhailov N. N., Remesnik V. G., Sidorov Y. G., Shvets V. A., Ikusov D. G., Varavin V. S., Yakushev M. V., Gumenjuk-Sichevska J. V., Golenkov A. G., Lysiuk I. O., Tsybrii Z. F., Shevchik-Shekera A. V., Sizov F. F., Latyshev A. V., Aseev A. L.

Opto-Electronics Review

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2019

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Vol. 27, No. 3

282--290

EN

We present an overview of our technological achievements in the implementation of detector structures based on mercury cadmium telluride (MCT) heterostructures and nanostructures for IR and THz spectral ranges. We use a special MBE design set for the epitaxial layer growth on (013) GaAs substrates with ZnTe and CdTe buffer layers up to 3” in diameter with the precise ellipsometric monitoring in situ. The growth of MCT alloy heterostructures with the optimal composition distribution throughout the thickness allows the realization of different types of many-layered heterostructures and quantum wells to prepare the material for fabricating single- or dual-band IR and THz detectors. We also present the two-color broad-band bolometric detectors based on the epitaxial MCT layers that are sensitive in 150–300-GHz subterahertz and infrared ranges from 3 to 10μm, which operate at the ambient or liquid nitrogen temperatures as photoconductors, as well as the detectors based on planar HgTe quantum wells. The design and dimensions of THz detector antennas are optimized for reasonable detector sensitivity values. A special diffraction limited optical system for the detector testing was designed and manufactured. We represent here the THz images of objects hidden behind a plasterboard or foam plastic packaging, obtained at the radiation frequencies of 70, 140, and 275 GHz, respectively.

2

Photoluminescence of HgCdTe nanostructures grown by molecular beam epitaxy on GaAs

Izhnin I. I., Izhnin A. I., Mynbaev K. D., Bazhenov N. L., Shilyaev A. V., Mikhailov N. N., Varavin V. S., Dvoretsky S. A., Fitsych O. I., Voitsekhovsky A. V.

Opto-Electronics Review

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2013

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Vol. 21, No. 4

390-394

EN

Photoluminescence (PL) of HgCdTe-based hetero-epitaxial nanostructures with 50 to 1100 nm-wide potential wells was studied. The nanostructures were grown by molecular beam epitaxy on GaAs substrates. A strong degree of alloy disorder was found in the material, which led to the broadening of the PL spectra and a considerable Stokes shift that could be traced up to temperature T~230 K. Annealing of the structures improved the ordering and led to the increase in the PL intensity. A remarkable feature of the PL was an unexpectedly small decrease of its intensity with temperature increasing from 84 to 300 K. This effect can be related to localization of carriers at potential fluctuations and to the specific character of Auger-type processes in HgCdTe-based nanostructures.

3

Defects in HgCdTe grown by molecular beam epitaxy on GaAs substrates

Izhnin I. I., Izhnin A. I., Savytskyy H. V., Fitsych O. I., Mikhailov N. N., Varavin V. S., Dvoretsky S. A., Sidorov Y. G., Mynbaev K. D.

Opto-Electronics Review

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2012

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Vol. 20, No. 4

375-378

EN

The Hall effect and photoluminescence measurements combined with annealing and/or ion milling were used to study the electrical and optical properties of HgCdTe films grown by molecular-beam epitaxy on GaAs substrates with ZnTe and CdTe buffer layers. Unintentional donor doping, likely from the substrate, which resulted in residual donor concentration of the order of 10¹⁵ cm⁻³, was observed in the films. Also, acceptor states, possibly related to structural defects, were observed.

4

Linear HgCdTe IR FPA 288 × 4 with bidirectional scanning

Vasilyev V. V., Predein A. V., Varavin V. S., Mikhailov N. N., Dvoretsky S. A., Gumenjuk-Sichevska J. V., Golenkov A. G., Reva V. P., Sabinina I. V., Sidirov Y. V., Susliakov A. O., Sizov F. F., Aseev A. L.

Opto-Electronics Review

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2010

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Vol. 18, No. 3

332-337

EN

The long wavelength (8-12 μm) IR FPA 288×4 based on a hybrid assembly of n+-p diode photosensitive arrays (PA) of HgCdTe (MCT) MBE-grown structures and time delay integration (TDI) readout integrated circuits (ROIC) with bidirectional scanning have been developed, fabricated, and investigated. The p-type MCT structures were obtained by thermal annealing of as-grown n-type material in inert atmosphere. The MCT photosensitive layer with the composition 0.20-0.23 of mole fraction of CdTe was surrounded by the wide gap layers to decrease the recombination rate and surface leakage current. The diode arrays were fabricated by planar implantation of boron ions into p-MCT. The typical dark currents were about 4-7 nA at the reverse bias voltage of 150 mV. The differential resistance R was up to R₀ = 1.6×10⁷ Ω zero bias voltage, which corresponded to R₀A ∼70 Ω •cm² and to the maximal value Rmax = 2.1 × 10⁸ Ω. The bidirectional TDI deselecting ROIC was developed and fabricated by 1.0-μm CMOS technology with two metallic and two polysilicon layers. The IR FPAs were free of defect channels and have the average values of responsivity Sλ = 2.27×10⁸ V/W, the detectivity Dλ * = 2.13 × 10¹¹ cm × Hz½ × W⁻¹, and the noise equivalent temperature difference NETD = 9 mK.

5

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.

6

Changes in 8-12 μm Hg₁₋xCdxTe photodiode arrays caused by fast neutron irradiation

Lysiuk I. O., Gumenjuk-Sichevska J. V., Dvoretsky S. A., Varavin V. S.

Opto-Electronics Review

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2010

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Vol. 18, No. 3

342-344

EN

We have measured the current-voltage characteristics of the long-wavelength infrared (LWIR) photodiode array, formed on the epitaxial Hg₁₋xCdxTe film (x = 0.21-0.23) with a high concentration of the Shockley-Read-Hall centres, before and after irradiating it with fast neutrons (energy 1 MeV, dose 5×10¹³ cm⁻²) at room temperature. Residual changes in current-voltage characteristics, persisting after 20 days, have been identified. Model calculations indicate that the Shockley-Read-Hall centre concentration increases 2-4 times, and the carrier lifetime decreases 2-5 times after the irradiation.

7

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.

8

320x256 HgCdTe IR FPA with a built-in shortwave cut-off filter

Vasilyev V. V., Varavin V. S., Dvoretsky S. A., Marchishin I. V., Mikhailov N. N., Predein A. V., Remesnik V. G., Sabinina I. V., Sidorov Y. G., Susliakov O. A.

Opto-Electronics Review

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2010

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Vol. 18, No. 3

236-240

EN

A photovoltaic detector design based on the graded band gap HgCdTe MBE structure with high conductivity layer (HCL) at interface, which provides photodiodes series resistance and a shortwave cut.off filter is developed. The optimal HCL parameters giving high quantum efficiency and minimal noise equivalent temperature difference were determined by calculations and experimentally confirmed. The hybrid 320x256 IR FPA operating in 8-12 μm spectral range was fabricated. The threshold power responsivity and minimal noise equivalent temperature difference values at wavelength maximum were 1.02x10⁻⁷ W/cm², 4.1x10⁸ V/W and 27 mK, respectively.

9

HgCdTe epilayers on GaAs : growth and devices

Varavin V. S., Vasiliev V. V., Dvoretsky S. A., Mikhailov N. N., Ovsyuk V. N., Sidorov Y. G., Suslyakov A. O., Yakushev M. V., Aseev A. L.

Opto-Electronics Review

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2003

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Vol. 11, No. 2

99-111

EN

View of basic and specific physical and chemical features of growth and defect formation in mercury cadmium telluride (MTC) heterostructures (HS's) on GaAs substrates by molecular beam epitaxy (MBE) was made. On the basis of this knowledge a new generation of ultra high vacuum set, ultra-fast ellipsometer of high accuracy and automatic system for control of technological processes was produced for reproducibility of growth MCT HS's on substrates up to 4'' in diameter. The development of industrially oriented technology of MCT HS's growth by MBE on GaAs substrates 2'' in diameter and without intentional doping is presented. The electrical characteristics of n-type and p-type of MCT HS's and uniformity of MCT composition over the surface area are excellent. The residual donor and acceptor centres are supposed as hypothetically tellurium atoms in metalic sublattice ("antisite" tellurium) and double-ionised mercury vacancies. The technology of fabricating focal plane arrays is developed. The high quality characteristics of infrared detectors conductance and diode mode are measured. Calculations of detector parameters predicted the improvement in serial resistance and detectivity of infrared diode detectors based on MCT heterostructures with graded composition throughout the thickness.

10

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.