High-quality AlN, GaN, AlGaN have been grown on sapphire substrate by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). The x-ray rocking curve of AlN and GaN were 100 arcsecs and 30 arcsecs respectively with Pendelloesung oscillations, which are the best reported to date. GaN with high crystallinity simultaneously exhibited high optical and electrical quality. Photoluminescence linewidth of GaN at 77K was as low as 17 meV, which is the best reported to date. Si-doped GaN had a mobility higher than 300 cm²/V.s. GaN has been also successfully grown on LiGaO₂ substrate with LP-MOCVD for the first time. AlGaN for the entire composition range has been grown. These layers exhibited the lowest x-ray FWHM reported to date. The excellent optical quality of these layers have been characterized by room temperature UV transmission and photoluminescence. N-type doping of AlGaN with Si has ben achieved up to 60 percent Al with mobility as high as 78 cm²/V.s. Al_xGa_1-xN/Al_yGa_1-yN superlattice with atomically sharp interface have been demonstrated. Optically-pumped stimulated emission in GaN:Ge and GaN:Si has been observed with threshold optical power density as low as 0.4 MW/cm². AlGaN photoconductors with cut-off wavelengths from 200 nm to 365 nm have been achieved for the first time. GaN p-n junction photovoltaic detector with very selective photoresponse have been demonstrated and theoretically modeled. Ti/AlN/Si metal-insulator- semiconductor capacitor with high capacitance-voltage performances at both low and high frequencies and low interface trap level density have been demonstrated for the first time in this material system.

Si-based heteroepitaxy is almost synonymous with strained layer epitaxy. The strain in a planar heteroepitaxial system is biaxial in the plane of the sample surface, and uniaxial in the direction perpendicular to the sample surface. It is to be differentiated from hydrostatic strain which has equal values in all directions. Strain plays a key role in device applications of the GeSi/Si heterostructures. However, it also imposes serious limitations on them. An almost universal constraint is the critical layer thickness for strain relaxation through dislocation introduction. Another potential problem, with strain is relaxation through 3D growth. For a given device application, whether the need is to relax or to utilize strain in the GeSi/Si heterostructure, control of MBE growth parameters is necessary to achieve the goal. The purpose of this review is to provide information of some key issues on how the device- important properties of the MBE grown silicon-based heterostructures can be controlled by the growth conditions. The considerations are based on the current understanding of the MBE growth physics of this material system.

The fabrication of HgCdTe IR detectors demands high-quality CdTe or CdZnTe substrates. Bulk CdTe tends to twin, therefore large single crystals are generally not available. This problem could be circumvented by growing CdTe epilayers on an alternative large area substrate. Several studies have been made on the growth of CdTe on different substrates such as InSb, GaAs, Si and sapphire by MOCVD and MBE techniques. We report the initial results for the growth of CdTe buffer films on GaAs (100) substrates by sputter epitaxy. This crystal was chosen as the substrate material because of its transparency to IR radiation and availability as large area wafers with high structural perfection. Epitaxial films of CdTe were deposited in a sputtering system with a base pressure of 2 X 10^-4 Pa. The GaAs substrate was degreased, etched in standard solution, and mounted immediately on a cooper substrate holder in the system. The substrates were ion etched in the sputtering system to remove surface oxide. The CdTe films were deposited in a wide substrate temperature range from 50 to 450 degrees C. Film thickness ranged from 0.1 to 5 micrometers , and deposition rates from 1 to 5 micrometers /h. The orientations and crystalline quality epitaxial films were characterized by x-ray diffraction. The surface morphology and the cross section of the gown CdTe layers were investigated by Nomarski interference contrast microscope. The optical and the electrical properties of the epitaxial films were investigated too. Structural characterization reveals that crystalline quality is a function of temperature of substrates. The single-crystals films grown at 300 degrees C on GaAs showed a best surface morphology.

The influence of the electromagnetic coupling between quantum wells on intersubband absorption spectra of multiple quantum well systems is discussed theoretically employing the effective medium approximation.

Photovoltaic effects from porous silicon (PS) based devices fabricated with electro-chemical etching processes have been investigated. Contact to the PS were made by bonding a small region of Al on a semi-transparent Au film. The structure of the uncoated porous layers were studied by SEM. Two levels of porosity were observed in n-type UV- and VIS-PS, surface etched features a few nanometers in diameter and macropores running deep in the bulk Si. Only nanopores were seen in p- type PS. The photovoltaic effects from the combination of the Au/porous Si junction and the PS/bulk Si heterojunction were observed under white-light of different intensity. The I-V characteristics of several PS based photovoltaic devices have been measured using a calibrated source. Photovoltages of the differently prepared n-type VIS-PS devices have been measured as a function of excitation energy. The polarities of photovoltage for both types of devices were found to be the same. P-type devices shows different I-V characteristics, depending on anodization current, all n- type PV devices present similar I-V characteristics.

Raman scattering line shapes have been calculated for 2D and 3D phonon confinements in porous silicon. The anisotropy of the optical phonon propagation was taken into account for Si, by using realistic phonon dispersion curves obtained by neutron scattering. The theoretical Raman spectra have been compared to the experimental results, and the prevailing nanocrystalline shapes and characteristic dimensions of wire- or sphere-like Si nanocrystallites in porous silicon were estimated.

Photoluminescence time resolved spectra (PL-TRS) and decay times measurements in microsecond range at room temperature on anodically etched boron-doped silicon are presented PL- TRS exhibit multiband structure and can be decomposed as a sum of few Gaussians. Decay curves of photoluminescence have a multiexponential shape. Relaxation times depend on wavelength of the observation. To explain our results we assumed model in which the multi-barrier structure is formed by silicon crystal surrounded by silicon quantum wires, oriented perpendicular to the sample surface with diameters in the range of 2 to 12 nm. The visible photoluminescence originates from radiative recombination between discrete energy levels in quantum well.

In this report we shortly summarize our research on free- and metallophthalocyanines of mono-, two-, three-, and four- valence metals. A crystallochemical systematization of unsubstituted phthalocyanines is reported. Also recent and therefore preliminary, but attractive results concerning iodinated phthalocyanine of five-valence arsenium are included.

Application of controlled local dissolution of multilayer thin film systems during electrochemical anodizing for forming of ordered nanosized structures is proposed. For producing approximately equals 0.1 micrometers microbulger systems the refractory metal (RM) - Al bilayer structures structures were used. Microbulgers of RM were obtained by anodizing bilayer structures. Microbulgers are shaped as Al₂O₃ pores, have 0.3 micrometers height and 4000 microbulgers/micrometers ² density. The degree of their ordering is estimated and determined using mathematical morphology operation erosion and dilation.

Elastic Recoil Detection and Rutherford Backscattering methods were used to obtain the depth profiles of hydrogen, oxygen and silicon atoms in porous Si layers on Si substrates. Large values of the oxygen concentration suggest a high oxidation degree of the specific surface of porous Si. It supports our earlier hypothesis, based on experimental evidence, that a formation of silicon oxidation oxides in porous layers is essential to the blue emission of light from this material.

Langmuir-Blodgett monolayers composed of bacterial reaction centers have been investigated by absorption, photoacoustics and time-resolved delayed luminescence in microsecond(s) time range.In reaction centers the excitation energy is able to initiate the charge separation process and then an electron movement across the monolayers takes place with high efficiency. The ability of reaction center to charge separation followed by the electron movement across the membrane could suggest it potential application in a molecular electronic device. Therefore, it is very important to follow the evolution of absorbed energy and its dissipation by radiative and non-radiative processes in such systems. These processes are competitive with the electron transport process.

The possibility of thin film material formation on the basis of silver acetylide organic derivative, 3-methyl-3-tert- butylperoxy-1-butynyl silver (PBS), was shown. It was used for photovisualization. The images formed in PBS thin films under UV irradiation were developed by two ways: thermally or using standard methol-hydrochinone developer.

Laser-assisted deposition technique (LAD) is analyzed as a method of obtaining high quality IV-VI and II-VI (HgCdTe) narrow-gap semiconductor thin layers and low-dimensional structures with abrupt metallurgical boundary and homogeneous impurity distribution in the layers. The basic structural, electrical, and electron paramagnetic resonance (EPR) of Mn²⁺ and Eu²⁺ in films and structures grown by LAD technique on different substrates at relatively low temperatures are analyzed. Using LAD technique with quasi-continuous regime of target evaporation by CO₂ laser (10¹ <EQ f <EQ 10³ Hz), where f is the modulation frequency of the laser beam in the transparency region of semiconductors used (hv < E_g) it was shown that the substrate temperature can be lowered to T approximately equals 300 K in the process of thin monocrystalline films and heterostructures growth. Several types of single crystal dielectric substrates with different lattice parameters a_o were for LAD technique of Pb_1-xSn_xTe, PbSe and Hg_1-xCd_xTe layers and structures growth. It was shown that even in the case of large lattice mismatch (Delta) a_o/a_o approximately equals 30 percent there exist technological conditions for growth of monocrystalline semiconductor layers. In dependence of substrate temperatures and laser power densities used for semiconductor targets evaporation the growth rate of layers in a vacuum chamber with residual vapor pressure of 10^-6 Torr was in the range of 10²-10³ angstrom/s.

The unique properties of thin amorphous diamond layers make them perspective candidates for producing advanced micro- electronic devices, coatings for cutting tools and optics. Moreover, due to the highest bicompatibility of carbon resulting from the presence of this element in human body, it appears to be a potential biomaterial. Until present the amorphous diamond has found industrial applications in some areas. One of the applications of the carbon layers are coatings for medical implants. The studies of carbon films as coatings for implants in surgery were aimed on the investigations of biological resistance of implants, histopathological investigations on laboratory animals, tests of corrosion resistance, measurements of mechanical properties and a breakdown test in Tyrod solution. The current state of published work in the subject is reviewed in the paper together with a discussion concerning classification of this material.

Amorphous carbon and nanocrystalline diamond layers are very interesting candidates for active and passive electronic and optoelectronic applications. One well knows that diamond films possess semiconductor properties. Because of their temperature stability, chemical inertness, large energy gap they are very perspective. The principal condition to apply them is not only to gain the high quality of the parameters but also to assure the stability of the obtained films' properties. The films discussed in this paper are deposited by r.f. dense plasma PCVD. To verify the structure quality it is sufficient to make quite easy measurements: ellipsometric ones and breakdown voltage. The structure image, on the level of ultra fine grains can be visible with the aid of atomic force microscope.

In the paper an assessment of the usefulness of a method for the formation of a hard carbon coating on the working surface of metal slitting saws has been presented. Metal slitting saws were used to cut off the tips of non-ferrous metals in printed-circuit boards. The results o the authors' own investigations concerning the assessment of life of metal slitting saws with modified geometry of the cutting edge and a hard carbon coating have been presented. Conclusions on the practicability of the RF PCVD method used have been formulated.

The TiN_1-xC_x thin layers were obtained by CVD technique using a flow method from reactant gas mixture: TiCl₄(g)-N₂(g)-CCl₄(g)-H₂(g). The obtained thin layers were investigated using metalographic, SEM and TEM techniques. Phase composition and lattice parameters were determined by the x-ray method using Inel, Philips and Siemens diffractometers. It was found that the morphology of the thin layers depends strongly on the temperature and time of deposition, type of growth substrate and also the molar ratios N/Ti and C/Ti in the reactant gas mixtures. Mirror- like and fine-grained thin films were obtained at temperatures of the growth substrate T <EQ 1100 degrees C. TEM examinations of the microstructure of the TiN_1-xC_x thin layers deposited on polycrystalline and single crystal Cu plates were also carried out. Factors responsible for the presence of a high density of dislocations in the examined layers were found. From DC measurements of resistance R in the temperature range 300- 4.2 K the residual resistance ratio RRR, superconducting transition temperature T_c, transition width (Delta) T_c and temperature coefficient of resistivity TCR were obtained.

Vacuum vapor deposited films of perylene-3,4,9,10- tetracarboxylic acid diimide derivatives (DPTA) permit to produce masks by laser vacuum projection lithography technique. The masks have submicron elements and plasma chemical etching (PCE) selectivity ranging from 7 to 15 during PCE of Si, SiO₂ and Al. Ion-beam sputtering (IBS) selectivity of the DPTA masks during IBS of Cu, Al, GaAs, alloys Cd_xHg_1-xTe and YBa₂Cu₃O_7-x by Ar⁺ ions with the energy of 700 eV were changed from 1.2 to 23.3. The influence of chemical structure of the compounds investigated on film IBS rate was discussed.

A brief review of the basic principles and the theory of scanning tunneling microscopy (STM) and spectroscopy (STS) as well as atomic force microscopy (AFM) is presented with emphasis on materials problem. The detailed spectroscopy and characteristic features of Bi₂Sr₂CaCu₂O₈ and Nd_2-xCe_xCuO_4-y (NCCO) single crystals in normal state are also discussed. In addition to STS studies, some examples of STM and AFM surface topography of NCCO single crystals are given.

Photoreflectance spectroscopy as the nondestructive, contactless, room temperature method to investigate semiconductor layers, interfaces, structures and devices is presented. Principles of the method are described. Application to the investigations of the III-V and II-VI compounds structures, including quantum wells, heterojunction bipolar transistors, high electron mobility transistors, vertical cavity surface emitting lasers and quantum dots arrays are shown.

Thick intentionally undoped GaAs epitaxial layers grown by LPE from Ga-Bi solution with different contents of Bi in liquid solvent were studied by photoluminescence at temperature T equals 2K. The dependence of photoluminescence spectra on contents of Bi in solution was analyzed.

InGaAs/GaAs quantum wells have been grown in MOCVD system equipped with horizontal Aixtron reactor. Photoreflectance spectra have shown, even at room temperature, sharp heavy and light holes excitonic transitions in quantum wells. The obtained splitting energies have been compared with values derived from theoretical considerations using envelope function model including lattice mismatch-related stress. Heavy and light holes transitions have been identified as excitonic transitions type I and type II, respectively. Photoluminescence measurements have been also done. For quantum wells, transitions between first heavy hole and first electron subbands have been observed. Additionally the temperature dependence of observed transitions have been performed.

Photoreflectance technique is used to investigate two types of GaAs/(AlGa)As heterostructures with 2D hole systems: triangular and rectangular quantum wells. The attention is focused on the few extra features visible above FKO oscillations. This extra features are found as a result of the 2D holes presence in our structures.

The photoluminescence (PL) spectra of MOCVD-grown GaAs samples have been measured at 10K, and for the most representative sample, PL spectra were recorded from 10 to 150K. Besides of the well-established transitions, a hitherto unreported peak was seen at 1.454 eV. The identification of a line at 1.408 eV is discussed.

We have measured the photoreflectance (PR) spectra at room and liquid nitrogen temperatures of two MBE grown GaAs/AlGaAs structures. The first one is HEMT type system with buried 10 periods of 2.5 micrometers GaAs/2.5nm AlGaAs superlattice. Oscillations-like signal associated with this SL have been observed and detailed analyzed. The second investigated structure is the sequence of 10 different quantum wells. Transitions in almost all wells and those associated with above barrier states have been observed. The experimental transitions are well described in terms of envelope function model.

This works focuses on the study of optical properties of Zn_xMg_1-xSe epilayers grown by molecular beam epitaxy on n-type (001) GaAs substrates. Luminescence, reflectivity and Raman spectroscopy are studied. Photoluminescence spectra of the samples are dominated by blue emission bands, which can be associated with radiative recombination of free excitons. The reflectivity spectra were used to investigate the refractive index value and the thickness of the layers. Moreover the temperature dependence of the band-gap energy of Zn_xMg_1-xSe epilayers was determined. Using Raman spectroscopy we can obtain information about two kinds of longitudinal optical phonon modes observed at room temperature, whose frequencies and intensities depend characteristically on Mg content.

Cleaved films of crystalline GaSe of thickness from 1500 nm to 5000 nm were investigated using optical transmittance, reflectance, photoconductivity (PC) and photoelectromagnetic effect. The investigations were performed, at room temperature for different illumination intensities and wavelengths. The oscillatory behavior of the measured spectral dependence is due to interference of radiation internally reflected in the samples were registered. The least square fitting of the experimental results with theoretical formulae allowed to determine the spectral dependencies of the real part of refractive index and absorption coefficient of radiation as well as the power coefficient in the power law dependence of PC on illumination intensity. The necessity of new theoretical description of he investigated effects is proposed.

Recently reported contactless photoelectromagnetic (PEM) method of determining carrier lifetime was used for the first time to measure carrier lifetimes in variously doped GaAs:Te, GaAs:Si as well as in multiquantum well structure grown on GaAs substrate. This method uses the dependence of PEM magnetic flux evoked in AC illuminated sample on frequency of chopping of the illumination intensity. In the presented experiments the samples were illuminated with radiation of different intensities and wavelengths emitted by diode lasers. The simple inspection of semiconductor wafer for laboratory and industrial purposes.

Spectral and kinetic properties of the electroluminescent thin film cells containing ZnS:Mn and Cu_xS layers were investigated. The cells were produced by thermal evaporation and chemical dipping. Kinetic measurements indicate that, for high manganese concentration the decay curve can be expanded in two exponentials. These exponentials are due to two kinds of manganese centers. Mn²⁺ ions and Mn²⁺-Mn²⁺ pairs. For low cells exhibit a reach structure in the blue and green spectral regions. Further investigation disclosed the presence of two types of the spectra. We also obtained a structure of manganese band of the electroluminescence of the cells for high manganese concentration. Similar to the short-wavelength bands, there are two types of the manganese bands. To our knowledge, this is the first observation of such structure of manganese bands at room temperature.

IR laser light scattering phenomena allows to visualize inhomogeneities in the bulk semiconductor materials. A device for observation of IR scattering in semiconductor wafers - the laser scanning tomograph (LST) - was designed and manufactured in the Institute of Applied Optics. A sample is illuminated by the diode pumped Nd:YAG laser, emitting the IR laser light in TEMoo mode. The laser beam diameter inside the semiconductor samples does not exceed 50 micrometers . The scattering centers inside the sample are observed perpendicularly to the direction of illuminating beam, using microscope with an IR CCD camera. To obtain a 2D image of scanned plane, the sample is moved horizontally by a scanning stage. The system has also a moving stage that allows to move the sample vertically. This enables the sample investigation in the third direction. The LST is controlled by a PC computer equipped with a user friendly software. The measurements results of GaAs wafers are presented.

Silver bromide crystals deposited on graphite were investigated with scanning tunneling microscope under ambient conditions. Different shape and size microcrystals, including cubic and octahedral forms and tabular grains, were observed and examined. Surface lattice parameters have been determined from high resolution images. In addition, the AgBr crystals were examined by scanning electron microscope.

The influence of hydrostatic pressure on the relaxation behavior of pseudomorphic Si_1-xGe_x samples were treated under high hydrostatic pressures at room temperature as well as at high temperature (900 degrees C and 950 degrees C). Annealing under high pressure causes both a strong increase of relaxation and a strong enhancement of the Ge-Si-interdiffusion with increasing pressure relative to annealing experiments under atmospheric conditions. The activation volume of the Ge/Si interdiffusion process is estimated.

Precise lattice parameters of stoichiometric TiN, TiC and Ti(N,C) solid solutions whiskers and needle-like crystals have been determined using the Bond's method. Temperature measurement of lattice parameters in the range 290-600 K have been performed and thermal expansion coefficients (alpha) have been determined. A non-linear change of coefficients (alpha) with the composition has been found. The observed decrease of (alpha) values for solid solutions crystals was related to the character of chemical bonds.

The results of x-ray diffraction and Auger spectroscopy of zirconium dioxide thin films are presented. These methods were used for studying the structural properties of zirconium dioxide thin films depending on the time and temperature range of thermal treatment. Super high-speed thermal treatment of metalorganic compositions of zirconium alcoholic solutions, Zr thin films and Zr anodic oxides thin films has been applied to prepare the samples which were annealed during 1-10s in situ at T equals 500 degrees C and higher at the rate of 80-250 degrees C/s with the following gradual cooling to the room temperature. The formed thin films have the following texture degree: anodic gradual cooling to the room temperature. The formed thin films have the following texture degree: anodic ZrO₂(Y₂O₃) - 98 percent. ZrO₂ formed by oxidation of Zr thin films - 71 percent, ZrO₂ formed from Zr metalorganic compositions - 100 percent. Auger analysis showed that anodic ZrO₂ thin films had the best barrier properties.

In this work we present results of investigations of the structure and electrical conductivity of 1,4-cis- polybutadiene. Roentgenography and thermally stimulated currents give information about phase transitions. Direct current conductivity was measured for thin films with Au and Al electrodes. The measurements were carrier out at the temperature range of 15-325K. The investigated material was 1,4-cis-polybutadiene of different content of the cis-form: 1. polybutadiene from ALDRICH 2. polybutadiene BR150 'Ubepol' from Philips Petroleum Corp. We observed influence of the internal structure on the electrical properties of the polymer. The Schottky and the Poole-Frenkel effect with hopping control the conduction of the material. determined activation energies are ranging from 0,3 to 0,36eV.

Results of measurements of electron drift mobility in polycrystalline structures of some simple aromatic hydrocarbons are presented. The mobilities are in the range of (1.1-3.3)-10^-5 cm²/Vs for the measurements in vacuum and (1.7-6.7)10^-4 cm²/Vs for the measurements in the air. The activation energies are of the order of a few hundredth of electronvolt. The results are interpreted in terms of hopping transport in a narrow band of localized states.

The temperature measurements of electric permittivity and pyroelectric current for polycrystalline Ba(Ti_1-xSn_x)O₃ - samples have been carried out. The decrease of temperature T_m of (epsilon) -peak and the increase of diffuseness of the paraferroelectric phase transition with the increase of x have ben observed. The overlap of three phase transitions into one for x > 0.06 has been observed.

Significant advances have been made in growing high quality HgCdTe detector arrays, designing and fabricating multiplexing readouts in submicron CMOS, and in subsequently fabricating large hybrid FPAs having excellent reliability. Consequently, high performance IR cameras are now being routinely developed for diverse applications. For example, FPAs as large as 1024 X 1024 with mean dark current < 0.1 e-/s, read noise < 0.1 e-/s and pixel yield as high as 99.85 percent for D > 1 X 10¹⁴ Jones are being supplied for IR astronomy. Affordable high performance IR imaging cameras, however, require cost-effective staring focal plane arrays (FPA) that operate at temperatures compatible with long-life, low-power coolers. We thus report a 5 micrometers 256 X 256 FPAs having mean D > 8.8 X 10¹¹ cm-(root)Hz/W with > 99.5 percent pixel operability at 90K operating temperature. The device's large charge capacity enables full coverage of the 3 to 5 micrometers atmospheric window to provide many of the advantages promised by competing staring LWIR sensors including enhanced S/N under stringent operating conditions and reduced background clutter. The staring Hg_1-xCd_xTe FPAs offer not only high sensitivity, operability and reliability at elevated operating temperatures, but also stable, temporal noise-limited imaging over the 3.4 to 4.8 micrometers passband. We report temporal sensitivity < mK with comparable spatial noise at 95K operating temperature. We also quantify the operating temperature stability required to maintain high sensitivity. Finally, we briefly status our HgCdTe FPA technology by focusing on key off-the-shelf CMOS readouts.

High performance PtSi Schottky-barrier focal plane arrays (SB FPAs) have been developed for thermal imaging by using a process technology fully compatible with silicon VLSI and an original readout architecture called Charge Sweep Device (CSD). Eliminating limitations of the conventional interline transfer CCD readout architecture, the CSD readout architecture makes it possible to design small pixels with high fill factors and large saturation levels. Thanks to a high fill factor of 71 percent and a large saturation level of 2.9 X 10⁶ electrons, a 512 X 512 element SB CSD FPA with a 26 X 20 micrometers ² pixel size has achieved a very low noise equivalent temperature difference of 0.033 K at 300 K with f/1.2 optics and a 30 Hz frame rate. A high- resolution SB CSD FPA with 1040 X 1040 pixels has also been developed. This high-resolution FPA produces HDTV- quality IR images at the standard TV frame rate. IR cameras with these FPAs have been used and proved to be useful for a wide variety of applications.

Recent trends in IR detectors are towards large, electronically addressed 2D arrays and higher operating temperatures. This will lead both to higher performance and to smaller, lighter and more affordable IR systems. Cooling requirements are the main obstacle to the more widespread use of IR systems based on semiconductor photodetectors, particularly in the civil field. Recently, there is a considerable interest for uncooled 2D arrays of thermal detectors for thermal imaging. The uncooled IR focal planes may revolutionize development of night-vision IR imaging systems. It is expected that the cost of IR imagers will be eventually reduced to a few thousand dollars or less.

Results of a study of the optical and electrical performance of P-on-n HgCdTe photodiode configuration are presented. The effect of doping profile and heterostructure contacts with wide gap region on the photodiode parameters is solved by forward-condition steady-state analysis. An isotype heterojunction, a high/low junction or very heavily doped high quality p-type material is required to achieve competitive performance from this device architecture in the diffusion limited temperature regime. It is shown that the isotype heterojunctions have the advantages over a high/low homojunctions for IR detectors. The wide gap region has low thermal generation rates of carriers and it also isolates the active region of the device from carrier generation at the contacts. Results obtained from computer simulations were found to be in qualitative agreement with previous experimental data on HgCdTe photodiodes.

In the paper, for the first time, the minority carrier diffusion lengths in a n-on-p and p-on-n GaN photodiodes have been estimated. The estimation procedure has consisted in adjustment of theoretically predicted spectral responsivity of GaN photodiodes to experimentally measured responsivity presented by Q. Chen et al. It has been found that due to the strong absorption of UV radiation in GaN material, the depleted region and the backside layer of the p-n junction have a minor for electrons in the p-type region and holes in n-type region, respectively.

In this paper, the growth of p-n InAsSb/InSb heterojunction using liquid phase epitaxy (LPE) has been discussed. The layers have been grown on B InSb substrate using an In-rich solution in horizontal slider type boat. The active InAsSb layer was first grown with a desired composition. The carrier concentrations in the top layer in the range 10¹⁶ cm^-3 to 10²⁰ cm^-3 was easily controlled using Cd doping. The standard structure consisted of 100 micrometers heavily doped n-type InSb substrate, an 10 micrometers InAsSb active region, and 2 micrometers heavily doped InSb p-type cap layer. Mirror like surface morphology was observed using a Nomarski differential interference contrast microscope. The structural characterization and the composition of InAsSb have been determined from x-ray diffraction data and IR transmission characteristic. The technology and construction of mesa photodiodes, both backside and frontside illuminated, have been presented. The analyses of the R₀A product and current-voltage characteristics as a function of temperature shows that the dark currents of InSb/InSb photodiodes are diffusion limited. At higher As composition the R₀A product is affected by the generation-recombination current of the depletion region.

The present high quality HgCdTe photodetectors are based on heterostructures with complicated band gap and doping profiles. Such structures can be obtained by combination of Isothermal Vapor Phase Epitaxy (ISO VPE) and RDF sputtering of CdTe. Cadmium Telluride exhibits unique properties - transparency to IR light, low conductivity, nearly lattice match and chemically compatibility to HgCdTe. Thus, low defect densities and hence low surface state density at the CdTe/HgCdTe interface are expected, which in turn lead to low surface recombination velocities and long effective lifetimes. The immediate use of CdTe epilayer is passivation of HgCdTe. High quality layers HgCdTe have been grown on CdTe substrates by open tube ISO VPE. CdTe layers have been obtained by RF magnetron sputtering on to previously deposited HgCdTe layers in 400 LS Leybold AG System. The substrate temperature can be varied form 20 to 90 degrees C. Thermal treatment has been performed in Hg/H₂ atmosphere in reusable chamber at temperatures 200-400 degrees C. The resulting heterostructures have been characterized by visual microscopy with Nomarski contrast, Hall measurements and IR transmittance. This technic and photolithography has been extensively used for successful fabrication of heterojunction contact photoresistors and heterostructure photodiodes.

Some aspects of the design of SAW acceleration sensors are investigated. The principles of operation are briefly reassumed. Our studies reveal that the cantilever beam is the optimum mechanical structure for the device. The calculations and experiments allow to determine the limits of applicability of lithium niobate as the substratum for the SAW acceleration sensor.

Investigations of thermoluminescence of lithium tetraborate activated with Dy, Mn and Eu and calcium sulphate activated with Dy caused by irradiation have been described. Both kinds of materials may be used in military and accident dosimetry.

In this work the optical and lasing features of 1.2at. percent neodymium doped GGG crystals in comparison to YAG, SLGO and YAP ones are presented. Influence of UV and gamma radiations on a change of absorption and luminescence spectra of the crystal is also reported. The strong influence of UV radiation of pump lamp on lasing characteristics of GGG:Nd crystals is stated. After cut off UV from pump lamp spectrum the slope efficiency of GGG:Nd laser can be placed between SLGO:Nd and SLGO ones.

In the present work the effects of gamma radiation on optical characteristics of Nd:SrLaGa₃O₇ crystals and results of examinations of lasing characteristics of gamma irradiated active elements made from the above crystals are reported. The increase of optical output was established for 'bad' rod. The possible mechanisms of radiation influence are discussed.

Transmission Line Matrix (TLM) is a numerical technique which can be used to simulate wide range of physical process. In the area of semiconductor device modeling the correct choice of electromagnetic analogue can have a strong influence on the stability, accuracy and efficiency of algorithms. This paper reviews recent progress in TLM with particular attention to the drift-diffusion process in carrier transport in semiconductors.

The kinetics of thermoluminescence (TL) and isothermal phosphorescence decay is studied by means of the MOnte Carlo method.It was shown that non uniform distribution of traps may significantly change the shape of the luminescence curves measured. The phenomena are especially important in dosimetric applications of TL where a sample is exposed to a high-energy radiation, which produces large defects - traps and recombination centers, most probably assembled into groups. In some of these cases the classical models developed for the theoretical description of TL spectra are inappropriate. It was found that using standard methods of analyzing TL spectra one can identify 'false' peaks - attributing them to non-existing trap levels.

Thermoluminescence (TL) is a powerful tool for studying trap structure of high-resistivity solids. However this phenomenon is especially known due to many practical applications in biology, industry, archaeology, etc. All the applications are based on the analysis of TL glow curves. For these purposes, relatively simple but credible methods are required. In this paper we consider the most acceptable trap model Taking advantage of some, recently derived analytical formulae, we present some new methods for determining trap parameters, especially the activation energy, from TL spectra. The methods are based on the analysis of the shape of TL curves and isothermal decay measurements.

The space-charge-perturbed currents (SCPCs) in insulators are studied for the case of arbitrary time dependence of the charge injection. The general formulae, determining the SCPCs for the time shorter than the first carrier transit time, are obtained. The special case of steady-state carrier injection is investigated both analytically and numerically.

The steady-state photoconductivity and photoconductivity decay have been measured from T equals 90 K to 310 K in n- CuInS₂ crystals. At high light intensities the dependence of photoconductivity ((Delta) (sigma) ) on excitation strength (L) is expressed by the relation (Delta) (sigma) approximately L^0.5. In this excitation strength range the decay of photoconductivity with time (t) can be described by the law (Delta) (sigma) (t) approximately (1 + Ct)^-1, where the constant C is proportional to the cross-section (S) for recombination of photoexcited free electron. From the (Delta) (sigma) (t) dependence the value of the cross-section was determined. The cross-section depends on the temperature according to the relation S approximately T^-1.

The fractional glow technique (FGT) developed by Gobrecht and Hofmann for determination of trap energy distribution in an insulating crystal is examined. The fractional thermoluminescence (TL) curves are generated by numerical solutions of the basic kinetic equations describing an insulator model with two kinds of interactive electron traps. The results show that two different activation energies of traps are resolved with the FGT when the corresponding individual TL peaks are not strongly overlapped.

The peak methods of Chen for the trap depth determination are applied to numerically calculated thermoluminescence curves of an insulator crystal. It turned out that the methods yield correct values of the trap depth except for the case of strong retrapping.