BaTiO₃ single crystals were obtained by Remeika-method from solutions of melted salts and oxides. Radioactive Co⁶⁰ isotope was employed as a source of γ-radiation. Three different radiation doses were applied: 1.2 x 10⁷ rad, 3.0 x 10⁸ rad, and 1.3 x 10⁷ rad. Temperature of single crystals during irradiation did not exceed 313 K. A few batches of crystals were subjected to irradiation, namely: single crystals with natural surface (after the crystal was grown), single crystals with the etched surface layer and single crystals which had been subjected to an influence of the strong direct and alternating electric fields before exposure. Both domain and defect structure of single crystals was investigated by the etching method, decorating method, optical microscopy and scanning electron microscopy. It has been found that irradiation causes destabilization of the domain walls of the head-to-head-type with a negative charge screening spontaneous polarization (P_s). The negative domains in a positive matrix, which did not grow through the whole crystal body, were found to decay under the influence of radiation. In a place previously occupied by decaying negative domains, defect clusters are observed. The investigations have shown that there is a close correlation between the domain structure and the defect structure of BaTiO₃ crystals.

PbTiO₃ crystal is a model ferroelectric material exhibiting perovskite-type structure, high Curie temperature (T_c = 765 K), large spontaneous polarization (P_s=0.42 Cm^-2) and electrical conductivity at T_c (σ_Tc =0.1 Ω^-1m^-1). A method of preparation of PbTiO₃ micro-crystals (size 1 - 50 μm) exhibiting isometric shapes and a method of segregating microcrystals into fractions within a narrow size range has been developed. The present work gives results of investigations on kinetics of the phase transition in micro-crystals exhibiting different dimensions. It has been found that P4mm ↔ Pm3m phase transition occurs in microcrystals in the presence of a single plane interface of {023}-type. During cooling of micro-crystals, the phase plane is followed by formation of the domain structure, which is a superposition of 180° dielectric domains and 90° domains (i.e. structural twins). The temperature hysteresis of position of the phase boundary is ΔT_PT ≈ 7K. Such a situation occurs in case of micro-crystals with dimensions larger than critical size (r_cr ≈ 20 μm). In case of r < r_cr the plane phase boundary is followed by formation of 180° domains only; the structure of 90° do not longer form. The thermal hysteresis also occurs but its value is two times larger (ΔT_PT ≈ 14 - 17 K).

In this paper we present our novel concept in bulk scatterometry of single crystals. A certain primary investigations have revealed both the polarizing and depolarizing properties of real defects. These phenomena are believed to have considerable influence on defects recognition in a future device proposed here. Apart of the linear polarizer on the input beam, and the adequate linear analyzers in the scattered light beams, a computer-driven monochromator will be used for revealing defects of different dimensions, thanks to the relation between the intensity of the scattered light and the wavelength. By using such a monochromator and the computer techniques, one should be able to plot 2-D and 3-D maps of crytalline defects, as well as an intenisty of scattered light as a function of wavelength for different points in the crystal.

Optical homogeneity (birefringence and birefringence dispersion mapping, transmission and additional absorption) was investigated on the entire areas of LiNbO₃ wafers doped with Cu ions and irradiated with protons of fluencies ranging between 10¹² and 10¹⁶ cm^-2. The birefringence dispersion studies have revealed a considerable influence of protons on LiNbO₃:Cu optical inhomogeneity, whereas the same influence on undoped LiNb0₃ was much less significant. The spectroscopic studies have revealed different mechanisms of defect formation depending on doses of protons. Also the secondary electrons generated by proton irradiation are believed to decrease the optical homogeneity by decreasing crystal's conductivity and generation of the color centers.

Recently, much attention has been paid to new crystals, which can be used as substrates for HTSC thin films. Among others (1-x)Sr(Al_0.5Ta_0.5)O₃:x LaAlO₃ (SAT_1-x:LA_x) crystals are very promising for microwave device applications, due to their lattice matching to the HTSC materials, thermal compatibility, low dielectric constant and very low dielectric loss at microwave frequencies at low temperatures. In this paper we report preliminary results of Raman and Brillouin scattering study of mixed cubic perovskites SAT_1-x:LA_x single crystals. The Raman scattering spectra have been obtained for SAT_1-x:LA_x crystals with LA content in the range: 0.23<x<0.3. Our results have been discussed in terms of LA content. Using Brillouin scattering method the velocity of the acoustic phonons propagating in [100] and [110] directions has been estimated at room temperature. The Debye theory and obtained values of the phase velocities allowed us to calculate Debye temperature.

The paper presents the results of complex investigations of the potassium-erbium double tungstate. The following properties have been measured: specific heat, specific heat in magnetic field, thermal expansion, thermal expansion in magnetic field, magnetization and X-ray structural data, reflectance and optical absorption spectra. The experiments were performed in the broad temperature range from 0.4 K to 300 K, spectral range from 4000 cm^-1 to 40000 cm^-1 and magnetic field up to 10T. The magnetic phase transition was found at temperature T=0.84K. In thermal expansion experiment the strong anomaly was found at T=7.6 K in magnetic field 10T. The KEr(WO₄)₂ belongs to the optical class of biaxial and pleochroic (trichroic) crystals. Using spectroscopy methods, the orientation of optical axes and refractive indices have been found. The main optical absorption spectra have been measured. The temperature dependence of optical absorption was determined.

In this work we present the results on synthesis of sol-gel produced compounds containing SiO₂ and MgO in different stoichiometric proportions. Tetraethoxy silane (TEOS), magnesium acetate, and dysprosium nitrate were used as precursors. After hydrolysis of TEOS in ethanol solution the other precursors dissolved in ethanol were added. After several hours the gelation process occurred, and transparent glass was formed. Subsequent heating at temperatures up to 1050°C led to formation of compounds containing SiO₂ and MgO: enstatite and forsterite. We checked the formation of relevant phases by means of X-ray powder diffraction. Thermoluminescent properties of the obtained compounds were checked after doping them with dysprosium ions. Linear response of thermoluminescent properties on gamma irradiation was found, but the sensitivity of phosphors obtained in this way was rather moderate comparing with other well known thermoluminescent phosphors.

This paper contains results of the researches upon new pyroelectric material: triglycine sulphate doped with theorine. Temperature dependences of complex dielectric permeability, spontaneous polarization, coercive field, and pyroelectric coefficient are presented as well as the measurement systems designed for determination of the mentioned above dependences.

This paper contains results of the researches upon relation between domain structure parameters and spontaneous polarization of new obtained ferroelectric material: triglicine sulphate doped with 10% L-Lysine (TGSL10). Model of domains structure distortion is presented. Basing on the model predictions samples were divided into three groups with different domain structure distortion parameter. Measurements of spontaneous polarization for the samples belonging to the mentioned three groups are also presented.

Low Noise Frequency Spectroscopy (LFNS) is a powerful tool for study of deep level impurities in semiconductors materials. The technique is based on analysis of generation and recombination noise. The number of free electrons in the conduction band may fluctuate, because of generation and recombination processes induced by traps. Measurement data are present as spectral noise density versus temperature at selected frequencies. The trapping and re-trapping processes in the sample manifest themselves by several noise peaks in measured noise spectrum. In LFNS method spectral noise density versus temperature for selected frequencies is measured. The analysis of spectral noise density versus temperature at selected frequencies is very promising -- in sample A eight traps were identified, in sample B six traps were identified. Low Noise Frequency Spectroscopy (LFNS) can be applied to characterization of both high and low resistivity materials.

The photoconductivity measurements of porous silicon were made using the visible light in wavelength range of 450 nm - 1200 nm. Obtained photoconductivity spectra were decomposed as a sum of Gaussian. The deep level energies are calculated for these peaks at about 1.24 eV, 1.33 eV, 1.55 eV, 1.84 eV, 2.17 eV and 2.54 eV at room temperature. To characterizing the deep levels we used also thermally stimulated depolarizaton current method (TSDC). In this case we used a thermal stimulation in temperature range of about 90 K - 300 K in vaccuum. After multigaussian decomposing of the current-temperature characteristic we calculated the thermal deep levels energies (0.4 eV and 0.8 eV). From the voltage-current measurements ideality factor was also calculated.

Photoluminescence (PL) spectra and excitation spectra (PLE) (under steady-state conditions), time resolved spectra (PL-TRS) and decay curves of photoluminescence (PL-DC) in micro- and nanosecond range (under pulsed operation) at different temperatures (10 K-room) on anodically etched boron-doped silicon are presented. PLE shows that visible PL is excited by light from UV region. PL and PL-TRS exhibit multiband structure and can be decomposed as a sum of few Gaussians. PL-DCs have multiexponential shape. Relaxation times depend on wavelength of the observation. To explain our results we assumed a model in which the multibarrier structure is formed by larger Si crystallites or wires (quantum well) surrounded by Si crystallites with diameters in the nanometer range (barrier region). The visible photoluminescence originates from radiative recombination between discrete energy levels in a quantum well.

The present paper deals with studies of deformation influence on Ge_xSi_1-x (x = 0.01 ÷ 0.03) whiskers conduction in the temperature range 4.2 ÷ 300 K. The whiskers were grown by chemical vapor deposition method in a sealed bromide system with use of Au and B dopants. The whiskers with resistivity ρ = 0.005 ÷ 0.025 Ω•cm were investigated. The values of resistivity corresponded to the impurity concentrations in the vicinity of the metal-insulator transition. The strain was imposed by the whisker mounting on specially selected substrates (quartz, copper, aluminum) with thermal expansion coefficient different from that in Si-Ge material. The 'giant' piezoresistance was found in the specimens at cryogenic temperatures. Estimated longitudinal gauge factor G <111> = Δρ/(ρ_oε) is equal to 10.000 ÷ 30.000 at 4.2 K in the whiskers with resistivity ρ = 0.012 ÷ 0.018 Ω•cm. From σ = f(1/T) curves activation energies for the hopping conductance in the whiskers have been calculated. Possible reasons of the obtained phenomena are discussed.

New structures aiming at controlling ferromagnetic properties of Diluted Magnetic Semiconductors quantum wells are presented. The carrier density is monitored by applying voltage in p-i-n diode or adjusting a distance between quantum well and surface. Surface doping was successfully applied to obtain samples with CdMnTe quantum well with up to 9.3% Mn concentration.

In this paper we report the result of investigation of the electrical transport in PLD grown n-PbSe/n-Si heterojunction by DC and AC current measurement techniques. This characterization method is a well-suited and simple technique to study the interface between two semiconductors. The Si substrates are highly doped (ρ = 0.45 Ωcm), and consequently most of the heterojunction depletion layer falls in the PbSe epilayer. Fabrication of PbSe thin films on Si substrates by the pulsed laser deposition(PLD) method has been demonstrated. The films were characterized by X-ray diffraction analysis.

This article reports the use of liquid phase epitaxy to fabricate buried HgCdTe photodiodes. Modern epitaxial techniques make possible to grow complex heterostructures with precise control of band gap and doping level profiles which can be applied for high performance optoelectronic devices. More complex heterostructures can be grown with 3 dimensional (3D) ban gap engineering using multiple epitaxy, selective growth, growth on profiled substrate and combination of these methods. We report an investigation of Hg_1-xCd_xTe epitaxial layers grown on holes etched in CdZnTe(111)B substrates. Prior to growth of HgCdTe layers the substrate has been etched to form holes on 30 μm diameter and 20 μm depth. Next, 20-μm thick HgCdTe epitaxial layer has been grown by liquid phase epitaxy (LPE) from Te-rich solution. The Nomarski microscopy showed that the surface of specially prepared layers was flat and the composition of layers measured by FTIR microscopy was homogeneous. Samples were cleaved and examined in cross section by SEM.

This paper describes and assesses growth of Hg_1-xCd_xTe (MCT) layers by liquid phase epitaxy (LPE) from Te-rich solutions by the tipping (rotating) method. Epitaxial layers with different compositions from x = 0.18 to x = 0.22 and thicknesses from 10 to 20 μm were grown on (111)B oriented CdZnTe substrates. Growth was carried out in the temperature range 460 - 480°C with cooling rates 0.05 - 0.1°C/min and under flowing H₂. The attention was paid mainly to the surface morphological quality, good decantation from the layers, uniformity of composition and thickness of films. HgCdTe layers were characterized using different methods: microscopic examinations, infrared microscopic transmission, secondary ion mass spectrometry and scanning electron microscopic measurements. By optimizing the growth parameters and construction of graphite boat it was possible to obtain high quality Hg_1-xCd_xTe photodiodes.

Polysaccharides like starch and cellulose derivatives, hydroxyethylcellulose (HEC) or hydroxypropylcellulose (HPC) were modified to obtain solid polymeric electrolytes. The chemical modifications were performed by the grafting of polymers with poly(ethylene oxide) mono and diisocyanates or JEFFAMINE (Shiff base). The physical modifications were made by the plasticization process of starch and cellulose derivatives with glycerol and ethylene glycol. All the samples obtained from polysaccharides were characterized by X-ray, thermal analysis (DSC) and impedance spectroscopy. The plasticized samples showed low glass transition temperatures (Tg); for HEC the value was about -60°C and for starch it was about -30°C. Tg values for grafted samples were of about -58°C for starch and -7°C for HPC. The low Tg values obtained are important to ensure good ionic conductivity that reached the values of about 10^-5 Scm^-1 for plasticized samples and 10^-6 Scm^-1 for grafted ones at room temperature. The good film forming and ionic conductivity properties of the samples of HEC, HPC and starch are very interesting candidates to be used as solid polymer electrolytes.

Epoxy resins are widely known due to their excellent mechanical properties, high thermal stability and high chemical resistivity. Recently, a new class of the materials was synthesized containing carbazole derivatives. This modification does not influence superior mechanical properties of epoxy resins, but significantly improves their luminous capacity. Absorption spectra exhibit edge at about 355 nm. Excitation at shorter wavelengths causes intense photoluminescence (PL) in UV and VIS region even at room temperature. This paper presents long-lived luminescence properties of carbazole derivative modified epoxy resins. These processes are competitive to PL. Therefore, in modified epoxy resins they are very weak. Phosphorescence decay (PD) and thermoluminescence (TL) experiments were performed using liquid nitrogen cooled CCD detection system. It allows measuring ultra-weak spectrally resolved luminescence in the range 200..1000 nm. The measurements were performed in a vacuum at different temperatures from 80 to 330 K. Phosphorescence and thermoluminescence spectra exhibit several emission bands indicating various recombination mechanisms. The kinetics of PD and TL was analysed using a new numerical technique that allows determination of characteristic activation energies and deconvolution of three-dimensional spectra for individual processes.

A series of porous carbon materials, produced by pyrolysis of saccharose and anthracene and heat treated at 1000°C, 1800°C and 2600°C has been studied by wide-angle neutron scattering. The neutron data were collected at Rutheford Appleton Laboratory (RAL). The data were recorded in the scattering vector range from 0 to 60 Å^-1 which enabled them to be converted to a real-space representation via the Fourier transform. The structure of these carbons has been described in terms of a model based on disordered, graphite-like layers with very weak interlayer correlations. At higher temperatures the anthracene-based carbon transforms into graphite while the carbon produced from saccharose remains disordered. The graphitization process has been studied in detail by careful analysis of the diffraction data in real and reciprocal space.

We have studied the temperature dependence (10K-325K) of the photoluminescence emission spectra (PL) under pulsed and continuous excitation and photoluminescence excitation spectra (PLE) under steady-state conditions of PPV (poly(p-phenylene vinylene)) layers fabricated by spin-coated deposition onto comercial indium tin oxide (ITO) coated glass and other substrates. The PPV organic polymer has an optical energy band gap about 2.5 eV and exhibits strong luminescence at all mentioned range of temperature and for different energy of excitation. PLE is wide and structureless in comparison to PL. PL spectra of PPV samples contain few peaks of vibronic origin in visible region. Position of peaks on energy scale depends on the temperature. We have observed red-shift of peaks with decreasing the temperature that results from changing of conjugation lengths in PPV molecular structure connected mainly with tensions between PPV layer and substrate.

Spectral behavior of chromic N-triphenylmethylsalicylidene imine in solid state has been investigated as function of temperature in 300-77 K temperature range. The analysis of the absorption, fluorescence and fluorescence excitation spectra together with the results of microscopic observation has been taken into account in monitoring of changing features. Direct evidence of the keto tautomer (open form) and intermediate formation has been presented, and dynamics of the intramolecular processes have been shortly discussed. The experimental activation energies equal to 5.9 kcal/mol and 9.5 kcal/mol have been extracted from the kinetics of thermally driven changes of luminescence. Those values have been attributed to 540-nm and 510-nm as well as 490-nm emitting species. Besides radiative transition, two main nonradiative deactivation channels, nonradiative transition and photochemical reaction, have been considered in explanation of the thermally enhanced photoactivity of the crystal under study. Contrary to a model anil compound, the photoactivity of studied molecular system with bulky substituent could be realized as dual-type behavior, thermochromic as well as photochromic simultaneously. The changes of the crystal color have been discussed in the frame of the proposed scheme. The scheme represents junction of thermochromic and photochromic behaviors following the proton transfer photochemical reaction acting as the first step of molecular rearrangement.

Typical analysis of thermoluminescence (TL) data is based on various curve fitting algorithms. Older methods used merely several characteristic points of TL curves as the peak position, inflection points or peak width. This approach is generally not suitable for advanced TL measurements utilizing simultaneous detection of wavelength and intensity of the emitted light. These data are represented in the form of surface in three dimensional coordinates. Spectrally resolved thermoluminescence (TL-3D) contains a lot of information concerning both trapping and recombination states. This new technique requires a novel theoretical approach for extracting from experimental data as much information as possible. In this paper we present new algorithm that we call the 'surface fitting.' TL-3D surface is numerically deconvoluted for individual peaks corresponding to trap levels and recombination centres. To demonstrate possibilities of the method we applied the algorithm to the analysis of TL-3D data of some thermoluminescence detectors based on LiF:Mg luminophor.

This paper is a brief summary of the technological development and state-of-the-art performance of quantum cascade lasers produced at the Centre for Quantum Devices. Laser design will be discussed, as well as experimental details of device fabrication. Recent work has focused on the development of high peak and average power QCLs emitting at room temperature and above. Scaling of the output is demonstrated by increasing the number of emitting regions in the waveguide core. At λ = 9 μm, over 7 W of peak power has been demonstrated at room temperature for a single diode, with an average power of 300 mW at 6% duty cycle. At shorter wavelengths, laser development includes the use of highly strain-balanced heterostructures in order to maintain a high conduction band offset and minimize leakage current. At λ = 6 μm, utilizing a high reflective coating and epilayer-down mounting of the laser, we have demonstrated 225 mW of average power from a single facet at room temperature. Lastly, these results are put in perspective of other reported results and possible future directions are discussed.

Performance of various possible designs of 400-nm nitride vertical-cavity surface-emitting lasers (VCSELs) has been analysed with the aid of the advanced three-dimensional (3D) thermal-electrical-optical-gain self-consistent threshold simulation. It has been demonstrated that it is practically impossible to reach the fundamental-mode operation in nitride VCSELs of the traditional design with two ring contacts. To enhance this desired operation, uniformity of current injection into VCSEL active regions should be dramatically improved. Therefore, we focused our research on designs with tunnel junctions and/or a semitransparent contact. In particular, it has been proved that the design with two cascading active regions, two tunnel junctions and a semitransparent contact may offer the most promising room-temperature performance characteristics for both pulse and continuous-wave operation. In particular, this design offers high mode selectivity with distinct fundamental transverse mode domination. Our simulations reveal, that the thickness and localization of a semitransparent contact as well as localization of active regions and tunnel junctions are crucial for a successful construction designing.

The French aerospace agency is involved in the realization of compact solid-state coherent sources, such as optical parametric oscillators (OPO), using new materials, such as highly non-linearly efficient semiconductors (ZnSe, GaAs or InP). However, since these materials are optically isotropic, they require new phase-matching techniques. We report the quasi-phase matched difference frequency generation in isotropic semiconductors using total internal reflection. We made use of large Fresnel birefringence at reflection between the signal and idler wave outputs of an OPO. Large tunability (between 8 and 13 μm) is demonstrated. Agreement between theoretical expectation and experimental results is excellent.

Modern communication in absolute secrecy requires creation of new intrinsically secure quantum communication channels. It is particularly necessary during the first connection between two parties establishing then in assumed unconditional security the secret cryptographic key which is supposed to be used afterwards during normal information exchanging. This new emerging field of quantum information technology is based on a new type of light sources, in which numbers of emitted photons can be carefully controlled. Especially advantageous are sources of single photons emitted at strictly predetermined moments, so called single-photon devices. Then any possible eavesdropper activity will be followed by some unavoidable disturbance which alerts both communication parties to an event. In the present paper, the Purcell effect associated with enhancement of spontaneous emission coupled to a resonator is explained, methods used to produce streams of antibunched photons are given, mechanisms applied to control carrier injection into quantum dots are shown and some possible designs of single-photon devices are presented and described. These devices are based on taking advantage of both the Purcell effect and the atom-like energy spectrum of quantum dots.

A new multilayer electrochromic device has been constructed according to the following pattern: glass₁/ITO/WO₃/gel electrolyte/BP/ITO/glass₂, where ITO is a transparent conducting indium tin oxide film having the surface resistance equal to 8-10 Ω. Tungsten oxide (WO₃) films were two-stage electrodeposited from the solution of sodium tungstate. To obtain a double layer, WO₃ film was first crystallized by annealing in the air at a temperature of 450°C for 1 hour, and subsequently, another WO₃ film was electrodeposited on it and annealing in the air at a temperature of 300°C for 1 hour. Obtained films had double layer structure: crystalline and amorphous/crystalline. Electrodeposited thin layer of prussian blue (PB) was a storage electrode of the device. A new gel electrolyte guaranteed high conductivity (σ = 4.8 mS•cm^-1). It consisted of 38% EC, 38% PC, 8% LiCF₃SO₃, 10% PMMA, 6% PEO, THF, where PMMA - polimethylmetacrylate, and poly(ethylene oxide)PEO - based polymers electrolytes, containing lithium triftalate - LiCF₃SO₃ and using mixed solvent of propylene carbonate (PC) + γ-butyrolacton (γ-BL). The electrochromic devices obtained in the research are characterized by considerable transmittance variation between coloration and bleaching state (25-40% at applied voltage of 1.5 to 3 V), and also high coloration efficiency (above 100 cm²C).

The advanced three-dimensional fully self-consistent optical-electrical-thermal-gain model of the 1.3-μm (GaIn)(NAs)/GaAs vertical-cavity surface-emitting laser (VCSEL) has been developed to simulate its room-temperature (RT) continuous-wave (CW) performance characteristics and to enable its structure optimisation. The standard GaInNAs VCSEL structure with an intracavity-contacted configuration exhibits very nonuniform current injection into its active region, whereas a uniform current injection is important in long-wavelength VCSELs for low threshold, high-efficiency and stable-mode operation. Therefore we decided to insert an additional tunnel junction within the active-region neighbourhood. The tunnel junction is shown to enhance effectively hole injection via a lateral electron current, with only a modest increase (a small penalty) in voltage drop and series resistance compared to standard devices.

Platinum silicide Schottky barrier detectors (SBD) and HIP-detectors GeSi/Si-based are widely used for application in the infrared spectral range. The increase in cutoff wavelength and responsivity of PtSi-Si photodevices is possible by formation of heavily-doped thin layer near to the semiconductor surface. The cutoff wavelength of HIP-detectors Ge_xSi_1-x/Si-based depends on x and concentration of boron in GeSi. In this report, the threshold properties of these detectors are considered. The dependencies of spectral detectivities and NETD from cutoff wavelength are calculated for various parameters of SBD and HIP-detectors. It is shown that optimal NETD of a SBD and HIP-detectors is possible for certain cutoff wavelength and temperature of detectors and depends on storage capacity. Also opportunity of formation of heavily-doped nanolayer in SBD detectors used by short-pulse recoil implanation of boron was studied.

A mathematical model of an ideal observation thermal imager (TI) is developed. At designing of model it was supposed: (1) The main noise source is a shot noise of photons irradiating a photosensitive element (PSE) of TI. (2) Temperature and reflection coefficients of objects under observation differ a little from the corresponding performances of the scence (background radiation). (3) Luminescence of the image of a local object area (LA) on a display screen of TI (useful signal) is determined by the difference between the electric charge accumulated in the canal PSE (optically conjugate with this local sites) and electric charge, accumulated in PSE canal, optically conjugated with the science. It was taken into account in the model: quantum efficiency of PSE, accumulation time in the PSE canal, the format of the array and PSE, parameters of a lens, losses in optical elements, mean temperatures and reflection (radiance) coefficients of the scene, temperatures and reflection (radiance)LA, counterradiation of the environment. Calculations (with consideration of counterradiation, angular sizes of objects, performances of objects and the scene) of utmost signal-noise ratio's; radiation noise equivalent temperature difference (NETD); radiation noise equivalent of reflection coefficients difference (NERD) for two spectral ranges: 3-5 μm and 8-14 μm. The quantitative evaluations of the influence of performances of environment on the listed above utmost parameters of TI for observation are obtained.

View of basic and specific physical and chemical features of growth and defect formation in mercury cadmium telluride (MCT) 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 MCT Hs's growth on substrates up to 4" in diameter. The development of industrially oriented technolgoy 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 metallic 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.

The performance of very long wavelength infrared (VLWIR) HgCdTe photodiodes at temperatures ranging from 77 K up to 150 K is presented. The effect of inherent and excess current mechanisms on quantum efficiency and dynamic resistance-area RA product is analysed. Different methods of determining the ideality factor are shown and among them the one based on the use of RA product versus bias voltage proves to be the most reliable. At higher temperatures, however, the calculated ideality factor does not give any useful information about the nature of the p-n junction current due to significant influence of the series and shunt resistances. A comparison of the experimental data with the results of analytical and numerical calculations shows that the photodiodes with cut-off wavelength up to 14.5 μm are diffusion-limited at temperatures exceeding 100 K.

The surface microrelief of CdHgTe layers grown by molecular-beam epitaxy (MBE) method has been studied by means of atomic-force microscopy. A periodic surface microrelief in the form of an ordered system of extended waves with the characteristic period 0.1-0.2 μm 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 system 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 waves 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.

The first results on a radiation stability investigation of mercury cadmium telluride (MCT) films, grown by molecular beam epitaxy (MBE) are represented. The samples were irradiated by high energy electron beams and gamma rays. Electrophysical and photoelectric parameters of MCT epilayers were measured. Volume material was measured too for the checking with MBE-grown one. MBE epifilms were irradiated on a pulsed electron accelerator with electron energy 1-2 MeV and current density less than 1 μA/cm² for several fluences. Also MCT epitaxial heterostructures were irradiated by Co⁶⁰ gamma rays. The same experiments were carried out for volume material. The analysis of dependence of Hall coefficient and conductivity from temperature and magnetic field (B) for p- and n- type samples was made. The irradiation of epilayers and volume MCT in the investigated range of irradiation fluences does not give both creation of electrical active damages in high concentrations and reconstruction of initial defects. Thus, MBE films of MCT have the high radiation stability to an electron and gamma irradiation. The obtained first results allow us to speak about high performance of explored MCT epilayers.

The researches on doping technology in HgCdTe LPE layers has become the crucial aspect concerned infrared photodiodes. This paper reviews incorporation and activation of dopants from IB, IIIA, and VA group as well as native defects in HgCdTe LPE layers grown from Te-rich solution. The work has been focused mainly on medium wavelength and long wavelength p-type layers because there is still a lot to do on this subject while n-type layers technology seems to be well established. The impurity issues like: segregation, coefficient, the energy and percentage of activation, and quasichemical approaches are discussed in order to explain impurity behaviour. Various kinds of anomalous of the Hall coefficient and electrical conductivity have frequently been experimentally observed, particularly in low band-gap material (x <0.2) with hole concentration less than 10¹⁷ cm^-3.

Investigations and comparative analysis of p-to-n type conductivity processes on the identical samples of vacancy doped p-Cd_xHg_1-xTe (x≈0.2) under IBM and anodic oxide annealing and on the identical samples of As-doped p-Cd_xHg_1-xTe (x≈0.22) under IBM and anodic oxide annealing have been carried out. The conversion of type of conductivity has been observed at the considerable depth of the vacancy doped material both under IBM or under anodic oxide annealing while in the case with As-doped material ony under IBM. It was considered that conversion in all these processes was determined by the mercury interstitial diffusion from corresponding mercury diffusion source and recombination with its native acceptors - cationic vacancies (in the first case) or with donor complex formations (in the second one). It has been shown that in the vacancy doped p-Cd_xHg_1-xTe the effective diffusion coefficients for the mercury interstitials that determines the depth of the converted layer are equal each other at equal temperatures either under thermal annealing in the saturated mercury vapour or anodic oxide annealing. It proves the identity of the mercury concentration in the diffusion source. Absence of the conversion under anodic oxide annealing in the As-doped p-Cd_xHg_1-xTe is explained by insufficient Hg concentration in the source and it matches well with necessary condition for donor complex formation as it takes place under IBM.

Narrow-gap semiconductor HgCdTe is one of the important elements used by the new IR-photonics. The well-developed technological methods suitable for preparation of different structures based on the material and high flexibility of the modern doping techniques made it possible to obtain materials with various properties. This article deals with some characteristics of photodiodes created by B ion implantation of this compound. Photoresponse of Hg_1-xCd_xTe+> -based photodiodes is investigated. The peculiarities observed experimentally can be determined by effects occuring in the region of n⁺-p-junction due to local inhomogeneity of boron impurity and irradiation defects taking place under the process of the diodes preparation. It has been found that the processes of transport and recombination of the injected minority carriers are effected by these inhomogeneities. Auger-recombimation is revealed as a dominant process in the interval of the impurity conduction. At the same time, the minority carriers' lifetime is decreased due to appearance of low-ohmic sections of the current registered experimentally. The form of the current pulse observed in n⁺-p-junctions is explained by electrons recombination in the base of the junction under forward direction of the current. Spectral and noise properties and kinetic characteristics of the HgCdTe-based photodiodes are also studied.