A concise review of the history and of the basic physics of the Wigner crystal (electron solid) in two dimensional electron systems in semiconductor heterostructures is given. The results of our experimental study on the formation and of the properties of the magnetic field-induced insulating phase, supposed to be a Wigner crystal, in a two dimensional gas in In_0.53Ga_0.47As/InP heterostructures are surveyed. These structures are characterized by a much greater disorder potential than AlGaAs/GaAs heterostructures due to the inherent alloy disorder in the InGaAs layer supporting the two dimensional electron gas. In high magnetic fields, below a Landau level filling factor of 0.4-0.5 divergent resistivity, non-linear current-voltage characteristics with a threshold, and a transition from non- activated to activated transport were observed. A model is proposed for the Wigner crystal-like ordering of the two dimensional electron gas in this system with large disorder.

X-ray diffraction and synchrotron x-ray topography methods were used to analyze strain in GaAs layers grown on GaAs and Si substrates by epitaxial lateral overgrowth (ELO) from a liquid phase. We show the laterally overgrown parts of ELO stripes adhere to the SiO₂ mask which results in their downwards bending. The procedure was found which allows to control adhesion of the layers to the mask by adjusting the vertical growth rate of the layers. For the case of GaAs ELO layers grown on Si substrates the ELO stripes bend outwards from the mask due to the tensile strain in the GaAs buffer layer. Recent data published on strain in other than GaAs ELO structures are reviewed and compared with our results.

Experiments on preparation of C₆₀ONCFn cycloadduct (Fn=ferrocene) and C₆₀(Cocp₂)₃ charge transfer complexes are described and their properties analyzed. The ferrocene derivative is bound to C₆₀ at the 6-6 bond by a heterocyclic oxygen-nitrogen-carbon ring. The experimental results are compared with the results of modeling using semiempirical quantum chemistry PM3 model. Scanning tunneling microscopy and spectroscopy has been used to observe variation of electronic structure along capped carbon nanotubes deposited on freshly cleaved HOPG(0001) surface. The electronic structure has been derived from measured dependence of tunneling conductance dI/dV on the applied voltage. The evolution of dI/dV(V) along the nanotube are discussed in terms of existing theories of nanotubes and quantum chemistry calculations.

We have studied the physical processes, which underlie the operation of a vertical quantum-dot nanodevice as a single- electron transistor. The Poisson-Schroedinger problem has been solved for the entire nanostructure. We have calculated the charge density on the quantum dot/gate electrode interface and the distribution of the ionized donors in n-GaAs layers close to the quantum-dot region. We have found that the characteristic rapid variation of the distribution of the ionized donors is responsible for the essential change of the electron confinement potential, which leads to a strong modification of the single- electron tunneling.

A simple theory of the quantum interference due to spin coherence and Larmor procession of the electron spin is proposed. A spin ballistic regime in a loop structure is assumed, where the phase relaxation length for the spin part of the wave function (L_phi^(e)) is much greater than the relaxation length for the orbital part (L_phi^(s)). In the presence of additional magnetic field, the spin part of the electron's wave function acquires a phase shift due to additional spin precession about that field. If also the structure length L is chosen such that (formula available in paper), it is possible to wash out the quantum interference related to the phase coherence of the orbital part of the wave function, retaining at the same time that related to the phase coherence of the spin part, to reveal the corresponding conductance oscillations. It is also emphasized that strong modulation of the conductance of the structure could be achieved in this way.

MBE-grown In (formula available in paper)As/GaAs double quantum dot structure has been investigated by photo reflectance (PR) spectroscopy. Features related to all the relevant portions of the sample including the quantum dots and wetting layers have been observed at 10 K. The PR results have been supported by the standard high-excitation photo luminescence (PL) measurements revealing excited state transition due to the effect of higher level filling. The experimental transition energies have been compared to the results of the effective mass approximation calculations for double quantum wells and lens-shaped double quantum dots. The evidence of the dot-dot and wetting layer well-well interaction has been found.

Results of the resistance studies on p-type germanium micro crystals grown in form of whiskers are presented. The crystals were brought to the vicinity of the metal-insulator transition (MIT) at liquid helium temperatures by doping with gallium and with some deep level impurities. A special technique has been developed to obtain these crystals anisotropically strained at cryogenic temperatures, so that both uniaxial tension and compression are achieved. The region adjacent to the MIT from both insulating and metallic side has been studied and some practical recommendations have been elaborated.

The epitaxial grown GaAs quantum wells (Qws) (with the width L₁=2.5nm and L₂=15nm) were subjected to alpha particle irradiation at doses (7.8*10¹²-3.4*10¹³)cm^-2. The response of the Qws was studied by means of the low temperature photo luminescence (PL) and inelastic light spectroscopy. The damage accumulation leads to a shift of the quasi particle energy level towards higher energy and to a decrease of the LO₁ and LO₂ modes and to an increase of the TO₂ frequency mode of the Al_0.3Ga_0.7As slabs.

Unexpected excess current was obtained in GaAs/InAs quantum dot structures at low temperatures and low current levels. This excess current exhibited instabilities with changing the bias, and over the time. It has been concluded that the excess current is a minority injection current connected with the high recombination rate through quantum dots. The instabilities are connected with unstable charge occupation of quantum dots.

Photoluminescence time resolved spectra (PL-TRS) and decay curves of photoluminescence (PL-DC) in the wavelength range 400-850 nm in micro and nanosecond time range at different temperatures (10K-room) on anodically etched boron doped porous silicon are presented. PL-TRS exhibit multiband structure and can be decomposed as a sum of few Gaussians. Positions of gaussian emission bands depend on temperature and change similar to thermal profile of the energy gap of the bulk silicon. PL-DC have multi exponential shape. Relaxation times depend on wavelength of the observation and temperature. At low temperature decay times dramatically increase (from few microsecond(s) at 300K to some hundred microsecond(s) ) and short component in nanosecond range has been observed. To explain our results we assumed model in which the multi barrier structure is formed by Si crystal (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 quantum well regions. Short component of decay at lowest temperatures is connected to non-radiative Auger relaxation inside porous silicon structures.

Amorphous nano-powders of Pb(Zr_0.5Ti_0.5)O₃ (PZT) solid solution were obtained by sol-gel method. As obtained nano-powders of mean dimension rapproximately equals 30 nm underwent consolidation by conventional ceramic sintering, hot high pressing, or rapid thermal annealing. As a result PZT ferroelectric ceramics exhibit lack of voids, density close to the theoretical X-ray density, homogeneity from both chemical and physical point of view and stoichiometric chemical composition. The nanocrystalline structure of the ceramics grains has been revealed by X-ray diffraction method. Dimension of the crystallites (Dequals20-75 nm) were found to depend on temperature (T_s) and the rate of sintering (v_T$. Of the sol-gel-derived powders. Dielectric and piezoelectric properties of the obtained nanocrystalline PZT ceramic samples varied with both sol-gel processing conditions and sintering conditions.

We report here on the development of host-guest and guest-guest interaction in course of preparation procedures semiconductor clusters (CdS, PbI₂), in zeolite (FAU,LTL) matrix. Optical properties of practically unexplored PbI₂/zeolite LTL system have been investigated. Both in absorption (reconstructed from diffuse reflection via Kubelka-Munk function) and luminescence spectra the features were observed at energies much exceeding the excitation resonance energy Eex in bulk PbI₂. This is considered as an indication of size quantization through the unambiguous attribution of the respective transitions requires further studies, including theoretical ones. For the samples with relatively high PbI₂ content the narrow emission peak only slightly blue-shifted from Eex was observed and attributed to long clusters formed inside the main channels of zeolite LTL lattice and possible retaining the layer structure of bulk PbI₂. The gradual disappearance of this peak during the storage of samples in the air is explained by assuming that originally formed long clusters undergo fragmentation into smaller species.

Nano structured Lu₂O₃, both plane and doped with Tb, was prepared utilizing a combustion technique. The best crystallity of the products can be obtained initiating the reaction within 560-700 $DEGC range of temperature. Tb easily enters the nano scaled host lattice both as Tb³⁺ and Tb⁴⁺. The former gives rise to a typical green emission of the ion, while the later introduces a broad-band visible absorption, due to charge transfer transitions. The green emission of Tb³⁺ from a raw material may be radically increased by after- preparation heat-treatment. Undoped material gives rise to a blue emission, which disappears when Tb content with respect to Lu reaches 0.0001% or higher level.

We present results of experimental investigations of Ni clusters deposited on ab surface of Bi₂Sr₂CaCu₂O_8+y (BSCCO) single crystals or highly oriented pyrolytic graphite (HOPG) substrates. The micro clusters were produced by the plasma gas condensation or evaporator with integral flux monitor. The scanning tunneling spectroscopy was performed at 24K and at room temperature. The spectra reveal differences between the curves measured above the Ni clusters and substrate, respectively. The relationship between surface atomic scale and local density of states in the materials is also discussed.

We report on a comparative investigation of as grown and alpha particle irradiated Ga-As-nipi doping super-lattices. We have used inelastic light scattering and low temperature photoluminescence spectroscopy to study the change in structural as well as electronic properties. Depending on the dose of alpha particles, we have found that the degree of structural damage varies. The PL spectroscopy shows that the main, e-Zn(h), band shifts toward higher energy (with a decrease in intensity). After annealing, partial recovery is found.

The polycrystalline thin diamond films grown by HF CVD technique have been studied by FTIR, ESR, X-ray, Raman and photoluminescence spectroscopy. Pl spectra were recorded in temperatures range of 10-300K. The thermal behavior of the broad band luminescence indicates a D-A pair recombination process. The defects taking part in luminescence can be associated with hydrogen related centers. The presence of hydrogen in the diamond layers has been confirmed by FTIR and ESR measurements.

PbSe thin layers were grown by pulsed laser deposition. The layers were obtained on Si substrates at temperature 45K to 650K. The structure of the layers and its lattice parameters were estimated from the X-ray diffraction measurements. The strong intensity of (200)-PbSe peak indicates a self-texture preference in the c-axis direction.

High resolution photo induced transient spectroscopy has been utilized to study defect centers in semi-insulating molecular beam epitaxy GaAs grown at temperatures 300 and 400 $DEGC. A number of traps with activation energies ranging from 0.004 to 0.64 eV have been detected. The traps are tentatively identified with native defects in GaAs lattice. The effect of the growth temperature on the defect structure of the layers is shown.

Deep states in semi-insulating Si are investigated by analyzing of two-dimensional Photo-Induced Transient Spectroscopy (PITS) spectra. The results exemplify new potentialities of the advanced computer programming technique.

The modulated photo current measurements (MPC) are performed in frequency domain. The excess charge carriers are generated by light source, the intensity of which is sinusoidally modulated. The phase shift between excitation and photo current is dependent on the frequency and temperature. The parameters of defect levels are estimated from this shift.

The technique of low frequency noise vs temperature is a powerful tool for study of deep level impurities in semiconductors materials. The physical parameters of the deep level defects are possible to identify from noise data. Measurement system to measure low noise spectra in frequency range from 0.01 kHz at temperature from 77K to 350K has been described.

Electrical properties of the electroluminescent thin film cells based on zinc sulfide were investigated. Current-voltage characteristics for whole electroluminescent cell and part of the cell were measured at room temperature. Current-voltage characteristics due to part of the cell were performed by point contact tunneling method. In both the kind of current-voltage characteristics memory effect has been observed. Different mechanisms of the charge transport through the cells and thin ZnS:Mn,Cu films were taken into account. We have found that it is more than one mechanism of electrical conductivity in the thin films.

In this work the results of m-terphenyl polycrystalline thin films investigations are presented. The main purpose of the investigations was to determine the mechanism of DC conductivity in the disordered m-terphenyl polycrystalline structures. The measurements were carried out for the thin films of m-terphenyl of the thickness varied from 2 to 13 micrometers with the presence of an external electrical field, which strength varied from 0 to 10⁶ V/cm. Applied temperature range was 15-325K. The investigated m-terphenyl thin films were supplied with either the gold and Aluminum or the gold and carbon electrodes. The determined values of activation energy were found to be in the range of kT to 0.2 eV. The study let us determine the influence of an external electric field on the height of the potential barriers between the trapped charge carriers. The results obtained as well as their analysis drive to a conclusion that an injection of an electric charge from the electrodes into the investigated material's bulk takes place through the thermoemission and field emission processes.

Results of an in-situ STM study of homoepitaxial copper electro deposition on Cu(111) in 0.01 M H₂SO₄ solution are presented which show a pronounced change in the growth and morphology of the deposit with increasing potential: while at - 0.40 V vs. SCE Cu multilayer growth is observed, Cu grows via a step-flow mechanism at -0.55 V. This behavior can be explained by the presence of an ordered sulfate adlayer at potentials >=-o.42 V, which causes a pronounced decrease in the Cu surface mobility.

New experiments are reported which explore the influence of the hydrostatic pressure during post-implantation annealing on the photoluminescence (PL) from silicon oxynitride layers (SiO_xN_y, x=0.25, y=1) implanted with Ge⁺ ions. It is shown that the use of a hydrostatic pressure during heat treatment results in an enhancement of the PL intensity by an order of magnitude compared with that arising from anneals carried out at atmospheric pressure. The observed increase in the PL intensity is explained in terms of the enhanced formation of radiative recombination canters within meta-stable regions of the implanted silicon oxynitride. The nature of these centers is believed to be associated with the equalsVSi-SiequalsV) center and defect complexes incorporating Ge atoms (e.g. equalsVSi-GeequalsV) or equalsVGe-GeequalsV) centers).

Principles and applications of the cantilever technique to measure strain and stress in thin films are presented. Different optical interferometers were created and applied to control stress-thickness dependence during technological processes or to measure two-dimensional strain distribution in thin film. An original scheme combining advantages of the classical interferometer and electronic speckle pattern interferometer is presented.

Magnetophonon Resonance in parallel transport of three types of Multiple Quantum Wells was studied. They consisted of ten QW of GaAs and ten AlGaAs barriers, and were obtained by the Metal Organic Vapor Deposition an semi-insulating GaAs. The MPR research were performed in pulsed magnetic fields up to 30 T. The transverse magneto resistance was measured between 77K and 340K and the MPR oscillations extracted by subtracting a voltage linear in magnetic field. The oscillating part of magneto resistance (Delta) (rho) _xx was recorded. A fine structure of MPR peaks was observed. This effect could be attributed to two phenomena: contribution of barrier phonons and influence of thermostresses.

Photoreflectance (PR) spectroscopy has been applied to the investigation of Si (delta) -doped Al_xGa_1-xAs layers grown by metal-organic vapor phase epitaxy on GaAs substrates. Measurements have been carried out on samples with aluminum content of 0,0.35 and 1. The observation of Franz-Keldysh oscillations (FKO) in a number of more than 10 (in the best case) and application of the fast Fourier transformation has allowed us to determine the internal electric field with high accuracy. Thus, the potential barrier between surface and (delta) -doped region has been estimated. Finally, the contribution of heavy and light hole related transitions to the FKO has been resolved.

The electrical and photo electrical behavior of Au/n-CdTe junctions prepared no CdTe mono crystalline substrates were studied. Both properties depended strongly on the parameters of the compensated high-resistive layer at the CdTe surface formed by annealing in air during preparation.

The effect of high temperature-high pressure (HT-HP) treatment of semiconducting layers on their structural properties was investigated by X-ray methods. The changes of the strain state of the samples induced by the HT-HP treatment depend on the initial strain state and growth method of thin layers. Only for the layers obtained by MBE methods the change of strain state of layers was found. Decrease of the dislocation density was detected for relaxed InAs/GaAs layers after the treatment at 673K - 1.1 Gpa for 1 h. For strained AlGaAs/GaAs samples the pressure - induces stress is responsible for creation of dislocation.

Substrate temperature is one of the important deposition parameters, which dictates many physical properties of thin films to a large extent. This paper deals with the effect of substrate temperature on the optical properties of Chromium films in the thickness range 5-80 nm. Soon after the growth the films were taken out of vacuum chamber and used in the transmittance measurements using DK2 Ratio Recording Spectrometer in the visible region of incident radiation, for both the films grown at substrate temperatures 27^DEGC and 180^DEGC. From the transmittance data of the films, we have evaluated the optical constants, refractive index, band gap and extinction coefficient for both the films. Using Lambert's Law the absorption coefficient is also calculated for both the films.

Spectra and kinetics of SnO_x-ZnS-Cu_xS-ZnS:Mn-Al electroluminescent cells were investigated for different dc voltage applied. Both zinc sulphide films and aluminum films were produced by thermal evaporation in a vacuum of about 10^-5Tr. The thin tin oxide films were prepared by spray technique, based on the pyrolysis of an aerosol on the surface of heated glass substrate. The Cu_xS layer was made by wet chemical process. The cells exhibit yellow-orange emission with a maximum at about 585 nm. Kinetic measurements indicate that the decay curve of the electroluminescence can be usually expanded in two exponentials. These exponentials are due to two kinds of manganese centers: Mn²⁺ ions with longer lifetime t₁ and Mn²⁺-Mn²⁺ pairs with shorter lifetime t₂. The values of the lifetimes depend on manganese concentration, temperature and types of crystal sites. The lifetimes are rather shorter for thin films and longer for crystals and powder phosphors. When a short voltage pulse is supplied to the cells, the maximum of the electroluminescence appears after the end of the exciting pulse. The phenomenon can be explained assuming energy transfer from one monomolecular center to another. The electroluminescence spectra were measured for several applied voltages from 18 to 100V. It was found that the spectrum becomes broader for higher voltages, mainly on the short-wavelength side of the spectrum. Additionally, the voltage dependence of the manganese lifetimes was investigated. The values of the lifetimes are longer for higher voltages.

The thin transparent and conductive Sn doped In₂O₃ layers have been deposited onto both surfaces of the glass plate of dimensions 0.2x16x16 mm using the constant-current ion sputtering method. In order to study the electron emission the voltage has been applied between both the ITO layers. One of the layers was 1 micrometers thick (the field electrode) and another one (10nm and much thinner) was deposited onto the opposite surface of the glass. This thin layer was treated as the electron emitter. The polarizing voltage U_pol has been applied to the field electrode. The study has been carried out in vacuum (10^MIN7hPa). The multichannel analyzer of amplitude of voltage pulses created by the electron multiplier has been used in order to record the electron emission yield. Aside of the field effects the studies concerning the result of UV illumination on the photo emission monitored by field has been examined. Determined were the amplitude spectrum of the voltage pulses for various polarizing voltage. The same method was used to find the dependence of the pulse frequency n on the applied voltage U_pol. The exponential dependence n = f(U_pol) has been found. The field induced emission mechanism can be explained on the basis of the well known phenomena occurring in semiconductors under influence of strong electric field (the hot electron effect, the impact ionization, the Gunn effect, the tunnel effect, etc.). It was also found that additional effect at simultaneous emission of two electrons as a result of absorption of a single photon have to be taken into account. The existence of this effect has been proved by decomposition of the amplitude spectrum into Gaussians. Measurements of electron energy in the field induced emission showed that about 80% of electrons have energy up to 10 eV. Photo induced optical second harmonic (SHG) has been also observed in these films.

The world at the end of the 20th Century has become blue. Indeed, this past decade has witnessed a blue rush towards the development of violet-blue-green light emitting diodes (LEDs) and laser diodes (LDs) based on wide band gap III-nitride semiconductors. And the hard work has culminated with, first, the demonstration of commercial high brightness blue and green LEDs and of commercial violet LDs, at the very end of this decade. Thanks to their extraordinary properties, these semiconductor materials have generated a plethora of activity in semiconductor science and technology. Novel approaches are explored daily to improve the current optoelectronics state-of- the-art. Such improvements will extend the usage and the efficiency of new light sources (e.g. white LEDs), support the rising information technology age (e.g. high density optical data storage), and enhance the environmental awareness capabilities of humans (ultraviolet and visible photon detectors and sensors). Such opportunities and many others will be reviewed in this presentation.

The development of devices for mid-, long-, and very long- wavelength IR detection has benefitted greatly from advances in band-gap engineering. Recently, there has been great progress in the development of n-type GaAs/AlGaAs quantum well infrared photoconductor (QWIP) detector arrays in all three technologically important wavelength windows. P-type GaAs.AlGaAs QWIPS represent a viable alternative to n-type GaAs/AlGaAs QWIPs, offering the advantage of normal incidence absorption without the need for grating couplers. The maturity of the MBE of GaAs/AlGaAs layered materials offers the possibility of mass producing low cost, high performance, large size, high uniformity, multicolor, high frequency bandwidth, two-dimensional imaging QWIP arrays. This paper describes progress in optimizing the performance of p- type GaAs/AlGaAs QWIPs through modeling, growth, and characterization. Using the 8x8 envelope-function approximation (EFA), a number of structures were designed and their optical absorption calculated for comparison with experiment. Samples were grown by MBE based on the theoretical designs and their photoresponse measured. P-type QWIPs were optimized with respect to the well and barrier widths, alloy concentration, and dopant concentration; resonant cavity devices were also fabricated and temperature dependent photoresponse was measured. The quantum efficiencies and the background-limited (BLIP) detectivities under BLIP conditions of our own p-QWIPs are comparable to those of n-QWIPs; however, the responsivities are smaller. For our mid-IR p-QWIPs, the 2D doping densities of 1- 2x10¹² cm^-2 maximized the BLIP temperature and dark current limited detectivity by operating at around 100K. At 80K, the detectivity of the optimum doped sample was (formula available in paper)at 10V bias. Barrier widths greater than 200 A were sufficient to impede the tunneling dark current; resonant cavities enhanced absorption five-fold.

The paper presents progress in infrared (IR) detector technologies during two hundred history of their development. Classification of two types of infrared detectors (photon detectors and thermal detectors) is done on the basis of their principle of operation. The overview of infrared systems and detectors is presented. Recent progress in different IR technologies is described from a historical point of view. Discussion is concentrated mainly on current and the most rapidly developing detectors: HgCdTe heterostructure photodiodes, quantum well AlGaAs/GaAs photoresistors, and thermal detectors. The outlook for near-future trends in IR technologies is also presented.

One of the simplest device realizations of the classic particle- in-the-box problem of basic quantum mechanics is the Quantum Well Infrared Photodetector (QWIP). In this paper we discuss the effect of focal plane array non-uniformity on the performance, optimization of the detector design, material growth and processing that has culminated in realization of large format long-wavelength QWIP cameras, holding forth great promise for many applications in 6-18 micron wavelength range in science, medicine, defense and industry. In addition, we present the recent developments in long-wavelength/very long-wavelength dualband QWIP imaging camera for various applications.

The paper reports on the design and fabrication of LPE-grown (formula available in paper) heterojunction photodetectors operating in the 2-2.4 micrometers wavelength region. Experiments on LPE growth of high-x- content quaternaries as well as optimization of device processing has been carried out. LPE growth at Tapproximately equals 530^DEGC enabled obtaining lattice matched heterostructures with 19% indium in the active layer In (formula available in paper) and photodetectors with (lambda) _co=2.25micrometers . By increasing the temperature of epitaxial growth to 590^{DEGC In (formula available in paper)heterostructures (with 23%indium content} suitable for photodetectors with (lambda) _co=2.35 micrometers have been obtained. Mesa-type photodiodes were fabricated by RIE in Ccl (formula available in paper) plasma and passivated electrochemically in (formula available in paper). These devices are characterized by differential resistance up to (formula available in paper) and the detectivity in the range (formula available in paper), in dependence on the photodiode active area cutoff wavelength.

We have studied spectral properties and photo potential/photo current generation in cyanobacterium Tolypothrix tenuis cells and their fragments in native and DCMU-treated samples. DCMU is known as an inhibitor of charge carrier process which is able to block the electron flow in photo synthetic apparatus. Since there is a competition among radiative, non-radiative and charge separation processes which lead to deactivation of excited states of molecules following spectroscopic methods have been used in the experiment: absorption, photo acoustics and photo voltage action spectrum (dependence of photo voltage on the excitation wavelength). Spectroscopic investigation was accompanied by photoelectric measurements for which specially photo- electrochemical cell constructed of semiconducting and gold electrodes with Tolypothrix tenuis suspended in polyvinyl alcohol (PVA) - water solution (15%v/v) and immersed between them was used. Kinetics of photo current have been examined in time of seconds. Thermal deactivation process in DCMU-free and DCMU- treated cyanobacterium is discussed and participation of various biliproteins and Chl (alpha) -complexes in light energy conversion is indicated. It has been shown the influence of DCMU treatment on the photo signal generation in Tolypothrix tenuis cyanobacterium. We have shown that Tolypothrix tenuis can be used in a system for light energy conversion into electric energy.

Photosensitivity of single and double heterostructures based on porous silicon was investigated. A number of double heterostructures were created by formation of the optical contacts on porSi/Si heterostructures and GeSe single crystal thin plate (d approximately 20micrometers ). Wide band photovoltaic sensitivity from 0.4 to 1.2 micrometers was observed for different heterostructures. The behavior of experimental curves was explained using energy band configuration. GaSe/porSi/Si heterostructures were also highly sensitive to mechanical stresses. It was concluded that heterostructures based on GaSe/porSi/Si plates might find their application as wide-band photo converters and tenzosensitive devices.

The material used throughout this study was Mercury Cadmium Telluride (MCT) grown by liquid phase epitaxy (LPE). Due to its special physical and electrical properties, MCT is still one of the most important infrared materials. That's why we are looking for the ways of improving technology and processing and then extracting the best of this material. This article concerns the influence of p-type MCT layer on junction formation during ion etching. To achieve device quality p-type layers, a lot of experiments were performed with annealing of as-grown wafers or adding different quantity of As to the melt. The technological problems with activation of arsenic and with ion etching are shown. Adjusting of parameters of annealing and etching processes allows n-on-p junctions to be formed with a controllable electrical profile. Standard techniques were used to determine optical and electrical parameters of layers.

This paper concerns HgCdTe heterostructure photodiodes for detection of infrared radiation from 8-12micrometers spectral range. Heterostructures were made by liquid phase epitaxy on the CdZnTe substrates. The cap layer of wider energy gap was used to suppress the generation-recombination current from the top contact. P-on-n junctions were placed in the narrow band-gap area close to the graded region. It was accomplished by appropriate selection of the cap layer thickness and adequate choice of parameters of the As diffusion process. Photodiodes were mesa delineated and illuminated through the substrate. Analysis of the impact of p-n junction location within a heterostructure, contact locations and mesa depth on photo diode parameters, was carried out. The experimental results were compared with two-dimensional numerical calculations performed in APSYS.

We have simulated a double barrier metal semiconductor metal (MSM) UV photo-detector based on a wide band-gap GaN layer deposited on a wider-gap AlGaN layer. Both M-S contacts were of Schottky barrier type. In order to perform the simulation the Poisson equation and the time dependent transport equations were numerically solved in a self-consistent way for the electrostatic potential, carrier concentrations, energy and photo current. Electron and hole transport as well as circuit elements are included. An examination was carried out of the response time of the photo diode when illuminated with the ultra-short pulses of UV radiation (2 picoseconds). The MSM structure was operated under DC bias when the UV pulse was absorbed in GaN in the region between the electrodes. The active area defined by the electrode spacing was chosen to be 0.5 and 1.5 microns. Co-axial cable was used. The current blocking AlGaN substrate layer was used to prevent photon generation far away from the electrodes. The results of simulation indicate that there is a very rapid response of the analyzed structure to pulsed UV radiation. At the DC small background a sharp spike of photo current appears. The influence of the between-electrode gap width on the MSM photo diode response was analyzed.

The results of investigation of PIN and MSM photo detectors fabricated in our Semiconductor Device Laboratory are presented. Discrete chips of PIN and MSM photo detectors and similar photo detectors integrated with a MESFET amplifier within a single MMIC chip were tested and compared. The structures were designed for range of wavelengths from 870nm to 1000nm. To accomplish this, the In_xGa_1-xAs absorption layer with appropriate cantent of indium has been used as an active layer. All structures have been fabricated using Metal Organic Vapor Phase Epitaxy (MOVPE) growth on GaAs substrates with the use of different buffer and matching layer configuration. I-V and spectral characteristics of the PIN and MSM photo detectors and also MMIC structures with the MSM photo detector were evaluated. Time response to the optical pulse excitation has been measured. All designs were compared from the point of view of their application in the optoelectronic integrated circuits.

Parameters of Hg_1-xCd_xTe epitaxial structures produced by molecular beam epitaxy are presented. Results of measurements of the carrier recombination lifetime, sensitivity and the noise voltage of photosensitive elements have been studied. A high detectivity was obtained over a broad wavelength range.

The photo electric characteristics of Schottky barriers, created by recoil implantation in silicon, are analyzed. Implantation of boron atoms in silicon samples was made by recoil method, inducing Al ion beams bombardment, with current density 4-10 A/cm² and 30-150keV energy. A SIMS analysis of obtained structures and calculation of their electric parameters show the opportunity of conducting layers formation, with a thickness of 10 nm and carrier concentration higher than 10¹⁸ cm^-3.

The abnormal photo electric properties of MIS structures in base of Si and HgCdTe, such as a significant photo-emf signal in enhancement and drop of the local photo-emf in inversion, were experimentally investigated. It has been established that the reason for the significant photo-emf signal in the state of enhancement and the related features of the photo electric properties of the Si-MIS-structure, is the photosensitivity in the region far from the electrode, associated with non-uniform distribution of electrically active defects in this region. It has also been established that the non-uniformity in surface potential (between the sub-electrode region and the region away from the electrode or between different points in sub-electrode region) may result in a drop of the local photo-emf in the state of inversion. A conclusion has been made that the redistribution of non-equilibrium carriers along the boundary must be taken into account in constructing equivalent circuits of the MIS structures.

A numerical technique has been used to solve the carrier transport equations for Hg_1-xCd_xTe and InAs_1-xSb_x photodiode operating near room temperature. The model calculates the spatial distribution of the electric field, the electron hole concentrations and the generation-recombination mechanisms. Also the effect of doping profiles on the photodiode parameters (R₀A product, detectivity) is analyzed. The R₀A product is controlled by a diffusion limited mechanism. In the case of HgCdTe photodiodes, only two processes of generation and recombination are important: Auger 1 and Auger 7; whereas in InAsSb photodiodes also the Auger S process has an essential significance. It is proved that Hg_1-xCd_xTe and InAs_{1- x}Sb_x photodiodes of optimum construction have similar detection parameters. This fact together with some advantages of InAsSb in comparison with HgCdTe indicates that InAsSb ia a potential competitor to HgCdTe as material for intrinsic detectors in the 3-5 micrometers and 8-12 micrometers spectral range.

2-(2'-hydroxy-5'-methylphenyl)-5-chlorobenzotriazole (TINCl) compound belongs to class of compounds in which after UV excitation intra-molecular proton transfer reaction takes place in solid state at room temperature. Newly created proton- transferred form flouresces in the red range of the spectrum. Microscopic study of micrometer size flourescing crystals gives an opportunity to observe guiding and amplification of spontaneously emitted light. Maximum of light traveling along the crystal is shifted towards high-energy range. We called this transfer in needle of spontaneously emitted luminescence as TINSEL effect. Taking into account the total internal reflection phenomenon, qualitative explanation of TINSEL effect was done. TINSEL gives new possibility of application TINCl as homogeneous core fiber.

The preparation of relatively large of acenaphthene, fluoranthene and pyrene crystals grown from vapor phase by plate sublimation method, is described. In order to characterize the intrinsic structure perfection of such grown crystals the X-ray examinations have been performed. The observed morphologies of these crystals have been compared with that predicted from PBC theory by Hartman-Perdok, model growth conditions (vacuum, temperature gradient) effect have been assessed.

Impurities present in commercially available naphthalene, fluoranthene and anthracene have been concentrated by zone melting and further evaporation of their extracts in chloroform, and identified by gas chromatography performed on CGC-FID and CGC-MS apparatuses. Quantitative contents of fourteen, eight and twelve impurities detected in naphthalene, fluoranthene and anthracene, respectively, have also been determined.

Based on the measured solubility data of acenaphthene, fluoranthene and pyrene in six halogen derivative solvents, the solutes activity coefficients ((gamma) s) have been determined from Scatchard-Hildebrand solution theory and used as a measure of solute-solvent interactions for determination of observed solvent effect on growth morphology and intrinsic structure of solution grown crystals of these hydrocarbons. The growth morphologies of these crystals have been interpreted on the basis of PBC theory assumptions. Correlation between activity coefficients of the investigated solutes and morphology as well as structure of obtained crystals, are found.