Infrared sensor designers have long maximized S/N ratio by employing pixel-based amplification in conjunction with supplemental noise suppression. Instead, we suppress photodiode noise using novel SoC implementation with simple three transistor pixel; supporting SoC components include a feedback amplifier having elements distributed amongst the pixel and column buffer, a tapered reset clock waveform, and reset timing generator. The tapered reset method does not swell pixel area, compel processing of the correlated reset and signal values, or require additional memory. Integrated in a 2.1M pixel imager developed for generating high definition television, random noise is ~8e- at video rates to 225MHz. Random noise of ~30e- would otherwise be predicted for the 5μm by 5μm pixels having 5.5fF detector capacitance with negligible image lag. Minimum sensor S/N ratio is 52dB with 1920 by 1080 progressive readout at 60Hz, 72Hz and 90Hz. Fixed pattern noise is <2 DN via on-chip signal processing.

Novel InAs/ InGaAs quantum dots-in-a-well (DWELL) infrared photodetectors are discussed. These detectors, in which the active region consists of InAs quantum dots embedded in an InGaAs well quantum well, represent a hybrid between a conventional quantum well infrared photodetector (QWIP) and a quantum dot infrared photodetector (QDIP). Like QDIPs, the DWELL detectors display normal incidence operation without gratings or optocouplers while demonstrating reproducible "dial-in recipes" for control over the operating wavelength, like QWIPs. Using femtosecond spectroscopy, long carrier lifetimes have been observed in DWELL heterostructures suggesting their potential for high temperature operation. Moreover, the DWELL detectors also have demonstrated bias-tunability and multi-color operation in the mid wave infrared (MWIR, 3-5 mm), long wave infrared (LWIR, 8-12 mm) and very long wave infrared (VLWIR, >14 mm) regimes. We have recently realized LWIR 320x256 focal plane arrays (FPAs) operating at liquid nitrogen temperatures. One of the potential problems with these detectors is the low quantum efficiency, which translates into low responsivity and detectivity. Some solutions to mitigate these problems are suggested at the end of the paper

The purpose of this paper is to present the electro-optical performances of dual-band detector working in a fully spatially coherent mode, with small pixel pitch. The successive steps of device fabrication are first exposed including molecular beam epitaxy, technological processing and readout circuit design. It is shown that very high quality multiple layer heterostructures of HgCdTe can be grown and processed into 256x256 arrays of 25μm pitch mesas, each mesa including two photodiodes with different cut-off wavelength ranging in the midwave infrared (MWIR). Characterization of these focal plane arrays (FPAs) shows very good homogeneity, low defect density and operabilities usually above 99% for both responsivity and noise equivalent thermal difference (NETD).

Some parameters of integration of a Quantum Cascade Detector (QCD) in an infrared imaging system are studied. Performances of QCD are first presented : absorption and responsivity spectra, peak responsivity (around 44 mA/W), resistivity at zero bias and detectivity. Quantum efficiency and photoconduction gain are deduced from these results. Finally the consequences of an integration of such a detector in a readout circuit are studied in terms of saturation of an external capacitor.

The first fully operational mid-IR (3-5 μm) 256x256 IR-FPA camera system based on a type-II InAs/GaSb short-period superlattice showing an excellent noise equivalent temperature difference below 10 mK and a very uniform performance has been realized. We report on the development and fabrication of the detector chip, i.e., epitaxy, processing technology and electro-optical characterization of fully integrated InAs/GaSb superlattice focal plane arrays. While the superlattice design employed for the first demonstrator camera yielded a quantum efficiency around 30%, a superlattice structure grown with a thicker active layer and an optimized V/III BEP ratio during growth of the InAs layers exhibits a significant increase in quantum efficiency. Quantitative responsivity measurements reveal a quantum efficiency of about 60% for InAs/GaSb superlattice focal plane arrays after implementing this design improvement.

The effect of interface anisotropy on the electronic structure of InAs/GaSb type-II superlattices is exploited in the design of thin-layer superlattices for mid-IR detection threshold. The design is based on a theoretical envelope function model that incorporates the change of anion and cation species across InAs/GaSb interfaces, in particular, across the preferred InSb interface. The model predicts that a given threshold can be reached for a range of superlattice periods with InAs and GaSb layers as thin as a few monolayers. The model also predicts that the absorbance for the 4 micron superlattices is inversely proportional to their period so that smaller period superlattices can be grown proportionately thinner. An added advantage of thin-period superlattices is a smaller hole mass and a lower Auger recombination rate, which should lead to higher detector operating temperatures. A number of superlattices with periods ranging from 50.6 to 21.2 Å for the 4 μm detection threshold were grown by molecular beam epitaxy based on the model design. Low temperature photoluminescence and photoresponse spectra confirmed that the superlattice band gaps remained constant at 330 meV although the period changed by the factor of 2.5. Overall, the present study points to the importance of interfaces as a tool in the design and growth of thin superlattices for mid-IR detectors for room temperature operation.

We report on our progress in research and development of ultrafast superconducting single-photon detectors (SSPDs) based on ultrathin NbN nanostructures. Our SSPDs were made of the 4-nm-thick NbN films with T_c ~11 K, patterned as meander-shaped, 100-nm-wide strips, and covering an area of 10×10 μm². The detectors exploit a combined detection mechanism, where upon a single-photon absorption, a hotspot of excited electrons and redistribution of the biasing supercurrent, jointly produce a picosecond voltage transient signal across the superconducting nanostripe. The SSPDs are typically operated at 4.2 K, but their sensitivity in the infrared radiation range can be significantly improved by lowering the operating temperature from 4.2 K to 2 K. When operated at 2 K, the SSPD quantum efficiency (QE) for visible light photons reaches 30-40%, which is the saturation value limited by the optical absorption of our 4-nm-thick NbN film. With the wavelength increase of the incident photons,the QE of SSPDs decreases significantly, but even at the wavelength of 6 μm, the detector is able to count single photons and exhibits QE of about 10^-2 %. The dark (false) count rate at 2 K is as low as 2x10^-4 s,^-1 which makes our detector essentially a background-limited sensor. The very low dark-count rate results in a noise equivalent power (NEP) below 10^-18 WHz^-1/2 for the mid-infrared range (6 μm). Further improvement of the SSPD performance in the mid-infrared range can be obtained by substituting NbN for another, lower-T_c materials with a narrow superconducting gap and low quasiparticles diffusivity. The use of such superconductors should shift the cutoff wavelength below 10 μm.

Narrow spectral band infrared detectors are required for multispectral infrared imaging. Wavelength selectivity can be obtained by placing passive line filters in front of the detectors, or, the preferred choice, by making the detectors themselfs wavelength selective. We review the first photovoltaic resonant cavity enhanced detectors (RCED) for the mid-IR range. The lead-chalcogenide (PbEuSe) photodetector is placed as a very thin layer inside an optical cavity. At least one side is terminated with an epitaxial Bragg mirror (consisting of quarter wavelength PbEuSe/BaF2 pairs), while the second mirror may be a metal. Linewidths are as narrow as 37 nm at a peak wavelength of 4400 nm, and peak quantum efficiencies up to above 50% are obtained.

We report on basic principle and technology of Si high-temperature (T>300K) IR emitter based on all optical down conversion concept. The approach is based on the possibility to modulate semiconductor thermal emission power in the spectral range of intra-band electron transitions through shorter wavelength (inter-band transitions) optical pumping (light down conversion process). Device emission bands are matched to transparency windows in atmosphere (3-5 μm and 8-12 μm) by adjusting thin film coat parameters. The carrier lifetime is responsible for the device time response whereas its maximum power emitted (mW-range) activates with temperature increase. One of the major advantages of devices employing optical "read in" technology is that they are free of contacts and junctions, thus making them ideal for operation at high temperatures.

A monolithically integrated low temperature MEMS and HgCdTe infrared detector technology has been implemented and characterised. The MEMS-based optical filter, integrated with an infrared detector, selects narrow wavelength bands in the range from 1.6 to 2.5 μm within the short-wavelength infrared (SWIR) region of the electromagnetic spectrum. The entire fabrication process is compatible with two-dimensional infrared focal plane array technology. The fabricated device consists of an HgCdTe SWIR photoconductor, two distributed Bragg mirrors formed of Ge-SiO-Ge, a sacrificial spacer layer within the cavity, which is then removed to leave an air-gap, and a silicon nitride membrane for structural support. The tuning spectrum from fabricated MEMS filters on photoconductive detectors shows high percentage transmission and a wide tuning range which is achieved with a tuning voltage of only 7.5 V. The FWHM ranged from 95-105 nm over a tuning range of 2.2 μm to 1.85 μm. Finite element modelling of various geometries for the silicon nitride membrane is also presented. The modelling is used to determine the best geometry in terms of fill factor, voltage displacement prediction and membrane bowing. The results of stress response of low-temperature plasma-enhanced chemical vapour deposited silicon nitride thin films to thermal cycling are also presented.

CdTe and HgCdTe layers were grown by MBE on GaAs(310) and Si(310) substrates. The dependences of microrelief height and macroscopic defects densities on the growth conditions of CdTe layer are plotted. CdTe buffer layers with the average height of surface relief of 2 nm are obtained. HgCdTe layers on GaAs(310) substrates with V-shaped defects density of 200-300 cm^-2 were grown. When Si(310) substrates are used, the boundaries between antiphase domains are an additional reason for formation of V-shaped defects. It is shown, that the optimization of surface preparation processes and the growth conditions allows to grow one-domain films of CdTe buffer layers on Si(310) substrates and to lower the density of V-shaped defects.

LWIR staring 384x288 focal plane array (FPA) has been developed and investigated. FPAs are manufactured on the basis of mercury cadmium telluride epitaxial layers grown both by liquid phase epitaxy (LPE) and molecular beam epitaxy (MBE). 384x288 FPA consists of a MCT photodiodes array formed in the p-type layer by ion implantation and silicon readout integrated circuit (ROIC). The photodiodes array pitch in each direction is 28 μm. ROIC performs the photocurrents integration during row period, signals multiplexing in two output channels from the focal plane. MCT photovoltaic array and ROIC are bonded by indium bumps. This photosensitive assembly is packaged in vacuum metal encapsulation and cooled down to temperature 80 K. Average detectivity was of 4.4^.10¹⁰ W^-1.cm^.Hz^1/2 for FPA cutoff wavelength of 10.7 μm. Test IR system on the basis of FPA was developed to obtain thermal images in real time mode at frame frequency 50 Hz. Test IR system performs two-point correction and defective elements replacement.

We report here the recent progress at VIGO/MUT (Military University of Technology) MOCVD Laboratory in the growth of Hg_1-xCd_xTe multilayer heterostructures for various types of uncooled infrared devices. The detectors are optimized for any wavelength within 1-12 μm spectral range. Hg_1-xCd_xTe growth with interdiffused multilayer process (IMP) technique has been improved. The total flow of the carrier gas was optimized to improve lateral uniformity of the composition and doping. The parasitic transient stages between the CdTe and HgTe phases were reduced to reasonable minimum. As a result, we were able to grow layers with homogeneous composition and doping, characterized by steep interfaces. The additional benefits were improved morphology, reduced dislocation density, and minimized consumption of precursors. The other issues addressed in this work were growth of heavy As-doped low-x and heavy Idoped high-x materials. Special modification to IMP process has been applied for in-situ control of stoichiometry. To maintain low vacancy concentration, special growth finish procedure has been developed. No post-growth thermal anneal was necessary for device-quality material. The MOCVD grown heterostructures have been successfully used for advanced uncooled infrared photodetectors such as multiple heterojunction photodiodes, multicolor and specially shaped spectral response multiabsorber devices.

The history and present status of the middle and long wavelength Hg_1xCd_xTe infrared detectors in Poland are reviewed. Research and development efforts in Poland were concentrated mostly on uncooled market niche. Technology of the infrared photodetectors has been developed by several research groups. The devices are based on mercury-based variable band gap semiconductor alloys. Modified isothermal vapor phase epitaxy (ISOVPE) has been used for many years for research and commercial fabrication of photoconductive, photoelectromagnetic and other devices. Bulk growth and liquid phase epitaxy was also used. At present, the fabrication of IR devices relies on low temperature epitaxial technique, namely metalorganic vapor phase deposition (MOCVD), frequently in combination with the ISOVPE. Photoconductive and photoelectromagnetic detectors are still in production. The devices are gradually replaced with photovoltaic devices which offer inherent advantages of no electric or magnetic bias, no heat load and no flicker noise. Potentially, the PV devices could offer high performance and very fast response. Actually, the uncooled long wavelength devices of conventional design suffer from two issues; namely low quantum efficiency and very low junction resistance. It makes them useless for practical applications. The problems have been solved with advanced 3D band gap engineered architecture, multiple cell heterojunction devices connected in series, monolithic integration of the detectors with microoptics and other improvements. Present fabrication program includes devices which are optimized for operation at any wavelength within a wide spectral range 1-15 μm and 200-300 K temperature range. Special solutions have been applied to improve speed of response. Some devices show picoseconds range response time. The devices have found numerous civilian and military applications.

Uncooled infrared focal plane arrays are being developed for a wide range of thermal imaging applications. Fire-fighting, predictive maintenance, process control and thermography are a few of the industrial applications which could take benefit from uncooled infrared detector. Therefore, to answer these markets, a 35 μm pixel-pitch uncooled IR detector technology has been developed enabling high performance 160 x 120 and 384 x 288 arrays production. Besides a wide-band version from uncooled 320 x 240 / 45 μm array has been also developed in order to address process control and more precisely industrial furnaces control. The ULIS amorphous silicon technology is well adapted to manufacture low cost detector in mass production. After some brief microbolometer technological background, we present the characterization of 35 μm pixel-pitch detector as well as the wide-band 320 x 240 infrared focal plane arrays with a pixel pitch of 45 μm.

SCD has recently presented an un-cooled detector product line based on the high-end VO_x bolometer technology¹. The first PFA launched, BIRD, is a 384x288 (or 320x240) configurable format with 25μm pitch. Typical NETD values for these FPAs range at 50mK with an F/1 aperture and 60 Hz frame rate. These detectors also exhibit a relatively fast thermal time constant of approximately 10 msec. In this paper we elaborate on the special advanced features that were incorporated within the ROIC and supporting algorithms. In this framework we have addressed two important issues: the power consumption and the time span between shutter activations. Minimum power consumption is a critical issue for many un-cooled applications. SCD has addressed this by introducing the "Power-Save" concept accompanied with flexible dilution architecture. The paper will present recent results exhibiting the various advantages. One of the limiting factors on the performance of un-cooled detectors is their vulnerability to ambient drift. Usually, even minor temperature fluctuations are manifested as high residual non-uniformity (RNU) or fixed pattern noise (FPN). As a result frequent shutter operations must be applied, with the risk of blocking the scenery in critical time frames. The challenge is thus twofold: increase the time span between shutter corrections and achieve better control of its activation. For this purpose BIRD provides two complementing mechanisms: A real-time (frame-by-frame) ambient drift compensation accompanied by an RNU prediction mechanism. The paper will discuss these features in detail and present illustrative system implementations.

This paper reports a novel uncooled infrared FPA whose performance is comparable to the cooled FPA's in terms of noise parameters. FPA consist of bimaterial microcantilever structures that are designed to convert IR radiation energy into mechanical energy. Induced deflection by mechanical energy is detected by means of optical methods that measures sub nanometer thermally induced deflections. Analytical solutions are developed for calculating the figure of merits for the FPA. FEM simulations and the analytical solution agree well. Calculations show that for an FPA, NETD of <5mK is achievable in the 8-12 μm band. The design and optimization for the detectors are presented. The mechanical structure of pixels is designed such that it can be possible to form large array size FPA's. Microfabrication of the devices, which can be improved to improve the performance further, employs low cost standard MEMS processes.

For over 27 years, SCD has been manufacturing and developing a wide range of high performance infra-red detectors, designed to operate in either the mid-wave (MWIR) or the long-wave (LWIR) atmospheric windows. These detectors have been integrated successfully into many different types of system including missile seekers, Time Delay Integration scanning systems, Hand-Held cameras, Missile Warning Systems and many others. SCD's technology for the MWIR wavelength range is based on its well established 2-D arrays of InSb photodiodes. The arrays are flip-chip bonded to SCD's analogue or digital signal processors, all of which have been designed in-house. The 2-D Focal Plane Array (FPA) detectors have a format of 320×256 elements for a 30 μm pitch and 480×384 or 640×512 elements for a 20 μm pitch. Typical operating temperatures are around 77-85K. Five years ago SCD began to develop a new generation of MWIR detectors based on the epitaxial growth of Antimonide Based Compound Semiconductors (ABCS). This ABCS technology allows band-gap engineering of the detection material which enables higher operating temperatures and multi-spectral detection. This year SCD presented its first prototype FPA from this program, an InAlSb based detector operating at a temperature of 100 K. By the end of this year SCD will introduce the first prototype MWIR detector with a 640×512 element format and a pitch of 15 μm. For the LWIR wave-length range SCD manufactures both linear Hg_1-xCd_xTe (MCT) detectors with a line of 250 elements and Time Delay and Integration (TDI) detectors with formats of 288×4 and 480×6. Recently, SCD has demonstrated its first prototype un-cooled detector which is based on VOx technology and which has a format of 384×288 elements, a pitch of 25 μm and a typical NETD of 50mK at F/1. In this paper we describe the present technologies and products of SCD and the future evolution of our detectors for the MWIR and LWIR detection.

Indium antimonide MWIR Focal Plane Array (FPA) have been developed and investigated. FPA consists of two dimensional arrays of InSb photodiodes bonded by indium bumps with CMOS-multiplexer and LN₂ cryocooler. Noise equivalent power NEP≈1×10^-12 W/pixel and dynamic range 60÷70 dB at frame frequency 250 Hz.

As a general tendency in the microelectronics field, the miniaturization of the products is more and more important and provides cost and system advantages. Following this general tendency, new InfraRed (IR) staring arrays are more and more compact and offer system solutions in the different IR wavebands. In France, the HgCdTe (Mercury Cadmium Telluride / MCT) material and process, as well as the hybridization technology, have been taken to the next even more advanced level of sophistication to offer these new staring arrays. Thus, for Mid Wave (MW) applications, a 15 μm pitch TV format (640×512) HgCdTe detector, called SCORPIO, is offered with a 1/4W micro cooler with miniaturized cryogenics. This optimized dewar has been extended to TV/4 format, using the successful focal plan array which is in mass production since 2000. Concerning Long Wave array, SOFRADIR has been offering for several years 320×256 LW detectors with a cut-off wavelength tuned between 9μm and 12μm depending on the required application. Based on that experience, two new LW HgCdTe products have been developed in 2004 and are offered since beginning of 2005. Relying on the standard HgCdTe production process with the latest improvements and on the optimized dewar family, VENUS-LW detector is now offered. This is a higher resolution 25μm pitch 384×288 LW IDDCA with a 0.5W micro cooler and with a cutoff between 9μm and 10μm for an operational temperature between 77K and 85K and for a spectral band pass fully satisfying the imagery requirements of compact LW FLIRs. This paper overviews the electro-optical and thermal performances of these three detectors and points out some reliability advantages of this new dewar design. Finally, the development trends for even higher resolution IR detector are discussed.

The work describes multiband photon detectors based on semiconductor micro- and nano-structures. The devices considered include quantum dot, homojunction, and heterojunction structures. In the quantum dot structures, transitions are from one state to another, while free carrier absorption and internal photoemission play the dominant role in homo or heterojunction detectors. Quantum Dots-in-a-Well (DWELL) detectors can tailor the response wavelength by varying the size of the well. A tunneling Quantum Dot Infrared Photodetector (T-QDIP) could operate at room temperature by blocking the dark current except in the case of resonance. Photoexcited carriers are selectively collected from InGaAs quantum dots by resonant tunneling, while the dark current is blocked by AlGaAs/InGaAs tunneling barriers placed in the structure. A two-color infrared detector with photoresponse peaks at ~6 and ~17 μm at room temperature will be discussed. A Homojunction or HEterojunction Interfacial Workfunction Internal Photoemission (HIWIP or HEIWIP) infrared detector, formed by a doped emitter layer, and an intrinsic layer acting as the barrier followed by another highly doped contact layer, can detect near infrared (NIR) photons due to interband transitions and mid/far infrared (MIR/FIR) radiation due to intraband transitions. The threshold wavelength of the interband response depends on the band gap of the barrier material, and the MIR/FIR response due to intraband transitions can be tailored by adjusting the band offset between the emitter and the barrier. GaAs/AlGaAs will provide NIR and MIR/FIR dual band response, and with GaN/AlGaN structures the detection capability can be extended into the ultraviolet region. These detectors are useful in numerous applications such as environmental monitoring, medical diagnosis, battlefield-imaging, space astronomy applications, mine detection, and remote-sensing.

A revolutionary technique for snapshot imaging spectro-polarimetry has been developed at the University of Arizona due to the recent availability of large focal plane arrays and greater computing performance on research workstations. The technique involves the combination of an imaging polarimeter with computed tomography imaging spectrometer (CTIS). This spectro-polarimeter uses modulation to encode the spectral dependence of all four Stokes parameters into a spectrum. CTIS is a snapshot imaging spectrometry method in which both spatial and spectral information is reconstructed using the inverse mathematical technique of medical computed tomography. The combination of these techniques provides the basis for a snapshot imaging complete Stokes spectro-polarimeter that can be implemented with no moving parts for the infrared spectrum.

The performance of p⁺-InAsSbP/n-InAs infrared (IR) photodiodes prepared by liquid phase epitaxy technique (LPE) is investigated. The current-voltage and capacitance-voltage characteristics, photoresponse and noise spectra are investigated in the temperature range 77-300 K. The trap-assisted current is calculated and compared with experimental data. It is found that at near-room temperatures and small reverse biases U ≤ 0.2 V experimental I-U characteristics are determined by diffusion and generation-recombination mechanisms. The trap-assisted tunnelling is shown to be dominant at higher reverse biases. The heterojunction photodiodes have superior photoresponse spectra in comparison with homojunction photodiodes and high threshold parameters.

The main features of p-n conductivity type conversion by ion milling in vacancy-doped p-Cd_xHg_1-xTe are considered. A diffusion model of the Hg interstitials source formation in MCT crystals under IM was proved through investigation of conversion depth dependence on composition. The model explains, both quantitatively and qualitatively, conversion depth dependencies on the IM temperature and the alloy composition. The most important factor, which defines these dependencies, is an electric field located at the interface between the p-type defect layer and the n type converted layer and in the grad band region. It was demonstrated that main features of carrier distribution over the p-n structure depth remained after 10 years samples storage. The relaxation of electrical properties of the n-layer main part after IM was explained by dissociation of donor complexes and centers formed by Hg interstitials with residual I and V group acceptor impurities. It was also demonstrated that IM results in forming a complex damaged n⁺-layer including several sub-layers with different nature of electron conductivity. An analysis of how electrons concentration relax in the n⁺-layer allows interpreting the nature of conductivity in one sub-layer through trapping mercury interstitials by dislocations and dislocation loops. The conductivity relaxation in this sub-layer occurs because the structure of such defects is rebuilt, with donor properties being lost.

Erbium (Er³⁺) and Ytterbium (Yb³⁺) ions doped Gallium Nitride (GaN) layers were deposited by RF magnetron sputtering. Deposition was carried out in Ar + N₂ gas mixture using Ga and Ga₂O₃ target as the source of Gallium. For the erbium and ytterbium doping, the Er₂O₃, Yb₂O₃ pellets, or Er and Yb powder were laid on the top of the Ga₂O₃ target. The GaN layers were deposited on silicon and Corning glass substrates. The properties of the GaN layers were investigated by using X-ray diffraction, Raman spectroscopy, absorption spectra and photoluminescence spectra. Prism coupling mode spectroscopy was used to measure the waveguiding properties. The composition of the fabricated samples was determined by using nuclear chemical analysis as Rutherford Backscattering Spectroscopy (RBS) and Elastic Recoil Detection Analysis (ERDA). The results of the experiments were evaluated in terms of the relations between the technology approaches and the composition and luminescence properties of the fabricated thin films. Up to now the best results, which can be utilized for a structure operating at 1550 nm (when pumped at 980 nm), were obtained when using (erbium plus ytterbium) metallic powder and Corning glass as the substrate for the deposition.

P-n conductivity type conversion under ion milling in MOCVD p-Cd_xHg_1-xTe/GaAs multi-layer hetero-structures is considered. It was revealed that CdTe (1 μm thick) passivation layer displayed the protective properties regarding ion milling action on active layer. P-n conversion at ion milling was observed in structures with 0.1-0.2 μm thick CdTe passivation layer; however, the converted depth (7 μm) was smaller than that in the similar homogeneous samples (15 μm). It was shown that the main properties of the converted p-n structures with thin CdTe layer were the same as in homogeneous samples. Ion milling resulted in forming of the typical n⁺- n - p⁺ structure with damaged n⁺-layer and main converted n-layer characterised by very low electron concentration. The relaxation of p-n structure electrical properties was also studied.

The electro-physical and photo-electrical properties of the HgCdTe/SiO₂/Si₃N₄ and HgCdTe/anodic-oxide film MIS structures is experimentally studied. The heteroepitaxial graded-band films Hg_0.78Cd_0.22Te were produced on the GaAs substrates by molecular-beam epitaxy. It was established of features of electrical properties were related with conduction type of the semiconductor and to the presence of near-surface graded-band layers. The test measurements of the electro-physical and photoelectric performances of MIS-structures in base of graded-band HgCdTe are held and the following parameters are found: resistances of volume, voltage of flat bands, densities of mobile and fixed charges, spectrums of surface states. It is shown that low-temperature double insulator SiO₂/Si₃N₄ is perspective for passivation of surface of focal plane arrays in base of HgCdTe-photodiodes.

In the paper experimental results on boron implantation of the Cd_xHg_1-xTe epilayers with various composition near surface of the material are discussed. The electron concentration in the surface layer after irradiation vs irradiation dose and ion energy are investigated for range of doses 10¹¹ - 3•10¹⁵ cm^-2 and energies of 20 - 150 keV. Also the results of the electrical active defects distribution measurement, carried out by differential Hall method, after boron implantation are represented. Consideration of the received data shows, that composition gradient influence mainly on the various dynamics of accumulation of electric active radiation defects. The electric active defects distribution analysis shows, that the other factors are negligible.

Results of research electrophysical and photoelectric properties of HgCdTe photoconductive structures grown by method molecular beam epitaxy under influence of background radiation are submitted. Strong dependence of photoconductivity and carriers lifetime for a level of background radiation (for change aperture angle of diaphragm), which come to an agreement with results of calculation for the Auger mechanism of recombination are represented.

InAs photodiodes were prepared by cadmium diffusion into substrates with n-type conductivity. Formation of compensated region with concentration of free carriers ~10¹⁵ cm^-3 is proved from measurements of barrier capacitance and transport mechanisms. The trap-assisted tunneling current is calculated for InAs photodiodes for the fist time. In this paper we proposed a model of the trap-assisted tunneling current which is caused by nonuniform distribution of impurity atoms and native defects. The trap-assisted tunneling current is caused by small areas of the junction which are characterized by increased concentration of defects and may be associated with dislocations, periphery of the junction or impurity fluctuations. Diffused photodiodes have higher threshold parameters in comparison with commercially available ones. Also, they exhibit higher photosensitivity in the short wavelength region due to existence of the surface built-in electric field.

In this paper the influence of low-energy Ar ion beam milling (IBM) on the properties of n- type Hg_1-xCd_xTe crystals has been studied. The as growth samples as well as these with thin Au layers deposited on the surface before irradiation has been investigated. The milling was carried out at room temperature and ions energy was 2 keV. In the initial samples the electronic properties of the near surface layer of 50 mm thick were changed. From Petritz model of the Hall results of two layer system the mobility and concentration of charge carriers in the modified layers were determined. In the samples with metal layer the doping caused by IBM is observed. In the case of Au the compensation phenomena is addressed. The model of defects created and theirs diffusion is discussed.

Effect of iso-valency doping with S, Se or Zn dopants on Hg_1-xCd_xTe mechanical, structural and photoelectric properties is considered. It was revealed that iso-valency doping reduced the etch pit density and increased the microhardness in Hg_1-xCd_xTe single crystals. Such doping also improved the photoelectric properties, especially increased the excess carrier lifetime. Taking into account the value of equilibrium concentration of S, Se and Zn iso-valency dopants in Hg_1-xCd_xTe single crystals it was concluded that the most suitable iso-valency dopant is Se.

Noise measurement is an important step in characterization of bolometers. Since this measurement is conducted with the bias applied to the bolometer and in most cases the measured noise level is well below the noise floor of FFT spectrum analyzers or other equipment used in this measurement, special pre-amplifiers and biasing circuits are needed. The requirements for these circuits are discussed in the paper along with limitations introduced by their components and the resistance of bolometers under test. Two preamplifiers, capable of measurements of bolometers whose resistance spans over five decades, are presented. Possible improvements to the existing pre-amplifiers are discussed and directions of further work are outlined.

Ultrasonically stimulated effects in Hg_1-xCd_xTe alloys were studied. Dependencies of Hall coefficient and conductivity of n- and p-MCT samples from temperature ( T=77÷300° K ) and magnetic field ( B=0÷0.7 T ) were investigated during ultrasonic influence and after ultrasonic treatment with frequency f_US = 5÷8 MHz and intensity W_US ⪝ 0.5•10⁴ W/m². It was shown that the action of the acoustic wave excited in Hg_1-xCd_xTe crystal by piezo-transducer results in an essential change of the carrier concentration up to change of the conduction type. The possible mechanism of sonic-stimulated effects was discussed in the frame of the intensive sonic-dislocation interaction model. The possibility of the thermooptical excitation of solid with activation of internal sources of the infrared radiation as a consequence of the acoustic wave energy absorption was determined.

Semiconductors containing so-called DX centers exhibit at low temperatures an ability to modify locally a refractive index under illumination. This modification persists due to the metastable character of the centers. As a result at low temperatures persistent photoeffects are observed for the materials. This property suggests the potential application of the materials in optoelectronic devices and an optical memory based on holography. It has been shown that at low temperatures the centers behave like deep defects whereas after photoionization they behave like shallow dopants. This twofold nature also accompanies different localization at the crystal lattice. As a result at low temperatures return to the "dark" ground state is not possible unless the system possesses enough energy. This energy is called the capture barrier. Changes in the refractive index depend on the height of the capture barrier and temperature. Estimation of the barrier is therefore of prime importance for materials possessing DX centers. It was found that a gallium dopant in Cd_1-xMn_xTe exhibits DX-like behaviour. In this paper we report on the capture barrier of gallium doped Cd_0.99Mn_0.01Te. In order to determine the barrier persistent photoconductivity (PPC) decay kinetics were investigated. The kinetics are governed by the transition from a shallow donor state to the deep DX state. The measurements were run within a temperature range from 77K