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This report results from a contract tasking A.F. Ioffe Physical-Technical Institute as follows: The contractor will investigate the relations between photoelectric and electric properties of several doped noncentrosymmetric crystals, mainly of iron doped lithium niobate crystals, LiNbO3:Fe, and their photorefractive properties. Photovoltaic effect, photo- and dark conductivity will be studied experimentally in parallel with studies of formation and other properties of holographic gratings in the samples of LiNbO3:Fe, which differ in the stoichiometry of the host (Li/Nb ratio), the concentrations of Fe ions, the Fe2+/Fe3+ ratios, and the concentrations of hydrogen. The experimental results and their theoretical analysis will allow the process of holographic grating formation in LiNbO3:Fe to be established on a microscopic level. The distribution of electric fields and charges in holographic gratings will be investigated spectroscopically and the microscopic structure of the Fe-centers dominant in photoelectric and photorefractive properties of LiNbO3:Fe crystals will be examined. Also, the photorefractive and photoelectric properties of strontium barium niobate, SrxBa1 xNb2O6 (SBN with x=0.61), will be studied. The proposed studies are to be conducted with the use of experimental facilities of the Solid State Optics Department of Ioffe Institute., The original document contains color images.

This report results from a contract tasking Ioffe Physico-Technical Institute of Russian Academy of Sciences as follows: The contractor shall numerically and experimentally investigate the processes accompanying pulsed magnetic impacts on a high-velocity flow of ionized gas, in particular, it's effect on drag and heat flux. The project is divided into the following 8 well defined tasks: Task1: Design and fabricate the model a flat plate with embedded electrodes. Adapt the algorithm and codes for the numerical simulation of an essentially non-stationary hypersonic flow of a viscous heat conducting plasma exposed to a pulsed magnetic field. Develop an acceptable design of the gradient heat flux sensor. Task 2. Choose the experimental flow regime and plasma parameters. Calculate the flow parameters in the test channel in a regime of an MHD generator. Task 3. Carry out measurements and calculations aimed at revealing the influence of a magnetic field on the heat flux toward the flat plate. Task 4. Analyze the experimental results, comparison with the results of calculations and make conclusions concerning an electrodeless scheme of the MHD interaction around a body of revolution. Task 5. Design and manufacture the model a body of revolution with an induction coil housed inside. Update the design of the gradient heat flux sensor: evaluation of the necessary sensitivity and placement. Task 6.- Mount the heat flux sensors and document the measurement system performance. Task 7. Search the test space of flow parameters and magnetic field strength that induce an electric current around the test object. Conduct numerical simulations of the MHD plasma flow about the test object. Task 8. Carry out measurements aimed at revealing the influence of a magnetic field on the heat flux toward the surface of a body of revolution. Analysis of the results., The original document contains color images.

This report results from a contract tasking Ioffe Institute as follows: The contractor will investigate the Distribution Function and Transport Properties of Charged Particles in Strong, Crossed Electric and Magnetic fields. The grantee will investigate a method to calculate the matrix elements of the Boltzmann equation collision integral for large values of the indices as well as arbitrary interaction potentials. This proposal is targeted for solving the transport problems in strong fields and would be very useful in the computation of weakly ionized plasmas and the extraction of cross-section data from experiments., The original document contains color images.

Electric-field effects in ESR spectrum of low-spin (S=1/2) tetragonal center Ni3+ was studied in KTaO3 single crystals. Orientation of the centers as well as splitting of the resonance lines was found resulting from the external E-field interaction with the electric dipole moment of the center. The value of the dipole moment was determined to be p=103D=21.4 eAngstrom. An analysis of the experimental results allowed us to make a reasonable choice of microscopic models for two nickel centers in KTaO3., Journal article submitted to Physics of the Solid State.

This report results from a contract tasking A.F.loffe Physical-Technical Institute as follows: High-power mid-infrared semiconductor lasers are of great importance for many applications such as laser diode spectroscopy, pollution monitoring low-loss optical communication medical diagnostics, etc. This project will introduce quantum wells into a heterojunction structure, as a means of obtaining near-room-temperature, high power mid-IR laser sources. Both experimental performance and means of fabrication will be investigated., The original document contains color images.

This report results from a contract tasking Ioffe Physico-Technical Institute as follows: As detailed in an on-line proposal the contractor will: 1) develop and build an optical device, fitted to a Fabry-Perot interferometer, to perform high-resolution quasieleastic light scattering spectroscopy; 2) develop related techniques for registering quasieleastic laser light scattering spectra; 3) measure temperature-dependent (77-300 degrees Kelvin) electrical conductivity to characterize metal/polymer/metal systems; 4) perform high-resolution Raman scattering mapping of epoxy/Al and teflon/Al interfaces to find quasalelastic scattering and the evolution of structural changes; 5) perform Brillouin light-scattering measurements on epoxy/Al and teflon/Al interfaces for evolution of the longitudinal modulus from the surface of polymer close to polymer/Al interfaces; 6) perform Rayleigh and quasielastic light scattering measurements on epoxy/Al. epoxy/Ag and teflon/Al interfaces to find the evolution of the relaxation time from the surface of polymer close to polymer/metal interfaces., The original document contains color images.

The flow separation phenomenon is encountered practically in all areas of technology related to liquid or gas flows. Generally, the separation leads to harmful consequences such as an increase of the body drag, a decrease of the wing lift, unsteady loads, and at high supersonic velocities causes emergence of narrow zones with intense heat fluxes toward the vehicle surface. The flow separation at supersonic velocities is associated with the interaction between shock waves and boundary layers. Shock-wave/boundary- layer interaction (SWBLI) has been a subject of many investigations over the past four decades aimed eventually at designing supersonic and hypersonic air intakes 1. There are some convenient physical models allowing the researcher to study SWBLI experimentally under simple conditions by means of a relatively simple visualization technique. One of such models is a supersonic flow inside an inner dihedral angle (compression corner). SWBLI may cause the flow separation in the vicinity of a compression corner. Improvement of understanding of the mechanism of the control of that interaction and prevention of the separation can pave the way for solving the problem of designing an air intake for operation over a wide range of the flight velocities. According to the AJAX concept 2, a magnetohydrodynamic (MHD) approach to controlling a supersonic flow of an ionized gas seems very attractive and advantageous., See also ADM001739. Presented at the Final Conference Proceedings on Thermochemical Processes in Plasma Aerodynamics held in St. Petersburg, Russia on 28-31 July 2003. EOARD-CSP-03-5031. The original document contains color images. Prepared in cooperation with Johns Hopkins Univ., Laurel, MD.

A frequency up-shift of twenty megahertz is observed in the interaction of a high power microwave (f(sub o)=2.84 GHz) with a magnetized inhomogeneous argon plasma. The dependencies of the frequency up-shift on the incident microwave power and frequency have been investigated. The induced up-shift is considered to be related to a rapidly growth plasma density in plasma wave guide., Pub. in International Conference on Phenomena in Ionized Gases (26th), v4 p183-184, July 2003. Prepared in cooperation with Institute of Molecular and Atomic Physics NASB, Minsk, Belarus. This article is from ADA421147 International Conference on Phenomena in Ionized Gases (26th) Held in Greifswald, Germany on 15-20 July 2003. Proceedings, Volume 4

The Bibliography Index `Nanodiamonds and Related Materials' was prepared for the First International Symposium on `Detonation Nanodiamonds: Technology, Properties and Applications'. It seemed important to us to introduce the Symposium participants to most of the recent publications, since the studies in the area of nanotechnologies - nanoelectronics, nanobioengineering and nanomaterials - are gaining greater importance in the modern world. A key position among nanomaterials belongs to nanocarbon clusters, such as fullerenes, nanotubes and carbon onions discovered at the end of the 20th century. Most of the papers included in the Bibliography are on detonation nanodiamonds. Two papers published in the Russian journal `Reports of the Academy of Sciences' and in `Nature' in 1988 are the most widely cited ones, so they are chosen as a zero point for the selection of publications. But we also included a short list of papers published before that date for the sake of historical reference. The publications on each topic are presented in a chronological sequence and in the alphabetic order within each year. The Index is concluded with a list of organizations and research groups involved in nanodiamond technologies, which may promote international cooperation within this community., ISBN: 5-93634-011-2.

This report results from a contract tasking Ioffe Institute as follows: The main objectives of the proposal include technological, structural, theoretical and electro-optical studies of the novel asymmetric III-VIII-VI hybrid heterostructures and fabrication of these structures as mid-infrared lasers. We are proposing a new physical approach consisting of combining III-V and II-VI compounds in the one hybrid asymmetric laser structure based on Al(Ga)SbAs/InAs/Cd(Mg)Se which will lead to large conduction and valence band offsets (in excess of 1 eV for both cases) providing strong carrier and good optical confinement. It will provide suppression of carrier losses from the active region of the laser and leads to better quantum efficiency and weaker temperature dependence of the threshold current of the new laser structure. Additionally, as an alternative approach, GalnAsSb/lnAsSbP asymmetric laser structures with high P content (more than 40%) will be grown by MOCVD and studied. Theoretical calculations of this new laser design will be performed. The main parameters of the novel hybrid III-VIII-VI mid-IR laser structure (temperature dependence of threshold current, spontaneous and coherent emission spectra, optical power in pulsed and cw mode) will be investigated. Such lasers should have applications to optical communication through the atmosphere, and materials processing., Original contains color plates: All DTIC reproductions will be in black and white.

This report results from a contract tasking Ioffe Institute as follows: The purpose of the proposed project is to develop, fabricate, test, and characterize silicon carbide power semiconductor opening switches operating in the picosecond range of switch time. Special SiC diode structures will be fabricated and investigated, including Junction Recovery Diodes (JRD). The operation of such diodes is founded on the superfast recovery of the junction's blocking ability after switching the device from forward to reverse bias conditions. Our estimations show that the parameters of JRD devices can be substantially improved in case of SiC devices, compared to both Si and GaAs capabilities. We expect i) to increase the speed of switch operation, the specific commutated power, and the operation frequency repetition; ii) to reduce the weight and size of pulse devices; and iii) to achieve better reliability of the devices due to the unique thermal conductivity and radiation hardness of SiC., The original document contains color images. All DTIC reproductions will be in black and white.

This report results from a contract tasking of the Ioffe Institute as follows: Historically Russian holographic research laboratories developed many unique materials having no analogs in other countries. This effort leverages that expertise and investigates two aspects related to correction of distortion of laser communications signals: 1. Development of the technique for compensation of atmospheric distortions in laser communication systems by means of dynamic holograms. We expect that depending upon the chosen holographic medium the following operational characteristics are attainable: Duration of a write/read/erase cycle - 1.0 msecond; Quality of correction - 80%; Improvement of the signal to noise ratio - 90%. The device will be automatic, real-time and reliable. 2. Development of a new holographic material based on self-developing dichromated colloids, for recording of stationary volume holograms. This task will include measurement of the optical effects caused by photo induced structural changes and hopes to achieve a resolution of up to 5000 l/mm and sensitivity down to 100 mJ/cm2., The original document contains color images.

A hybrid double heterostructure with large asymmetric band offsets, combining AlAsSb/InAs (as a III-V part) and CdMgSe/CdSe (as a II-VI part), has been proposed as a basic element of a mid-infrared laser structure design. The p-i-n diode structure has been successfully grown by molecular beam epitaxy (MBE) and exhibited an intense long-wavelength electroluminescence at 3.12 micrometers (300 K). A II-VI MBE growth initiation with a thin ZnTe buffer layer prior to the CdMgSe deposition results in a dramatic reduction of defect density originating at the II-VI/III-V interface, as demonstrated by transmission electron microscopy. A less than 10 times reduction of electroluminescence intensity from 77 to 300 K indicates an efficient carrier confinement in the InAs active layer due to high potential barriers in conduction and valence bands, estimated as delta E(sub c) = 1.28 eV and delta E(sub v) ^ 1.6 eV. An increase in the pumping current results in a super-linear raising the EL intensity. The type of band line up at the coherent InAs/Cd(1-x)Mg(x)Se interface is discussed for 0 <- <- 0.2, using experimental data and theoretical estimations within a model-solid theory., Pub in: Materials Research Society Symposium Proceedings, Volume 692. This article is from ADA405047 Progress in Semiconductor Materials for Optoelectronic Applications Symposium held in Boston, Massachusetts on November 26-29, 2001.

(In)GaAsN based heterostructures have been found to be promising candidates for the active region of 1.3 micron VCSELs. However (In)GaAsN bulk layers and quantum wells usually demonstrate lower photoluminescence intensity than their nitrogen-free analogues. Defects associated with lower temperature growth and N-related defects due to plasma cell operation and possible nonuniform distribution of nitrogen enhance the non-radiative recombination in N-contained layers. We studied the photoluminescence intensity of GaAsN layers as a function of N content in MBE grown samples using rf-plasma source. Increasing the growth temperature to as high as 520 deg C in combination with the increase in the growth rate allowed us to avoid any N-related defects up to 1.5% of nitrogen. Low-temperature-growth defects can be removed by post-growth annealing. We achieved the same radiative efficiency of GaAsN samples grown at 520 deg C with that of reference layer of GaAs grown at 600 deg C. Compositional fluctuations in GaAsN layers lead to characteristic S-shape of temperature dependence of photoluminescence peak position and this feature is the more pronounced the higher the amount of nitrogen in GaAsN. Annealing reduces compositional fluctuations in addition to the increase in the photoluminescence intensity. The results obtained are important for farther improving the characteristics of InGaAsN lasers emitting at 1.3 micron., Pub in: Materials Research Society Symposium Proceedings, Volume 692. This article is from ADA405047 Progress in Semiconductor Materials for Optoelectronic Applications Symposium held in Boston, Massachusetts on November 26-29, 2001.

We report on a room temperature detector which allows to determine and monitor the state of polarization of torahertz radiation with picosecond temporal resolution. The detector is based on the circular photogalvanic effect recently observed in GaAs/AlGaAs quantum wells. The circular photogalvanic effect yields in response to elliptically polarized radiation a current signal proportional to the degree of circular polarization. The peak current signal occurs in unbiased samples for circular polarization, vanishes at linear polarization and changes sign by switching the helicity from right-handed to left-banded. The detector consists of a (113)A MBE grown p-GaAs/AlGaAs multiple quantum well structure. The response has been measured in the wavelength range between 76 micrometers and 280 micrometers at normal incidence of the radiation on the sample., Pub in: Materials Research Society Symposium Proceedings, Volume 692. This article is from ADA405047 Progress in Semiconductor Materials for Optoelectronic Applications Symposium held in Boston, Massachusetts on November 26-29, 2001.

Semiconductor alloys are unstable at critical temperatures because of the positive enthalpy of alloy formation. The critical temperature of decomposition is the function of elastic parameters which differ due to structure relaxation of epitaxial film. It opens the new way to vary the critical temperature and the phase diagram., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

An influence of MBE growth parameters (substrate temperature, total group V flux, and As/Sb flux ratio) on a composition of Al(x)Ga(1-x)As(y)Sb(i-y) alloys (x = 0.5) as well as their structural quality have been studied in detail. Using these data, As and Sb incorporation coefficients have been calculated in two different ways. An effect of the unintentional Sb incorporation in InAs layers is also discussed., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

Three-dimensional opal-Si composites with both direct (a variable extent of filling of opal voids with Si) and inverted structures have been synthesized. A structural analysis of these fabricated systems is performed. Reflectance spectra from the surface (III) of the composites are measured. Observed spectral features are interpreted as a manifestation of the direction III photonic band gap that is tunable in position and width in the visible and near-infrared spectral ranges., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

In conclusion we present a new and direct electrostatic force microscopy method to resolve the electric field and capacitance distributions in laser diodes. Using this method we have investigated the fine structure of the electric field in AlGaAs/GaAs and InGaP/GaAs p-i-n based laser diodes under forward and backward biases. We have also found a strong increase in the capacftance at the waveguide under forward biases. We believe that this effect is related to the carriers injection into the waveguide and can be used to study the injected carriers distribution., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

This report documents a detailed XRD study of the novel type-II CdSe/BeTe nanostructures formed by stressor-assisted self-formation. High sensitivity of the diffraction curves to interface types is revealed. The model developed for a sinmilation of rocking curves includes spontaneous formation of BeSe enriched interface formation when the smaller amount of CdTe FM stressor as compared to that corresponding to a maximum RHEED SSI is intentionally deposited., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

Changes introduced by a photonic bandgap environment in an emission spectrum of a light source have been compared for direct and inverted opals and a qualitative difference has been revealed., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

Electron density and high-frequency (hf) hopping conductivity of two-dimensional electron gas (2DEG) in SI delta-doped GaAs/AlGaAs heterostructures are studied by acoustic methods. In the quantum Hall regime at small filling factors both quantities appear dependent on the cooling procedure characterized by an initial temperature T (o) of a fast cooling to 4.2 K by immersing into liquid He. These facts are interpreted assuming that T (o) is the freezing temperature for the conductivity of the delta-layer which supplies electrons to 2D channel., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

Fabry-Perot a-Si:H/a- Si:O:H microcavities with Er-doped a-Si:H active region were fabricated by plasma-enhanced chemical vapor deposition technique. A metalorganic compound was used to incorporate erbium into the active a-Si:H layer. The room temperature transmission, reflection and spontaneous emission spectra of the microcavities with 2 and 3 pairs of layers in distributed Bragg reflectors are measured. An intensity enhancement by two order of magnitude and selective narrowing of the 1.54 micrometer erbium emission line was observed as compared to the case of a single a-Si(Er):H film deposed on a quartz substrate. A theoretical analysis of the experimental data presented is given., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

In the present work we have carefully optimized the operation of plasma source and the growth parameters of GaAsN layers. We have demonstrated the possibility of incorporation about 1.5% of N into GaAs without decreasing the photoluminescence intensity., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

We report the first experimental observation of folded acoustical modes in strained hexagonal GaN/A1(x)Ga(1)(-x)N superlattices by Raman scattering. The dispersion of LA phonon branch was determined by using different scattering configurations. It was found that the zone center gap of folded phonon branch is beyond the instrumental resolution (approximately equal 0.5 cm (-1)) The sound velocity for GaN/A1(x)Ga(1)(-x)N SL with Al content x= 0.28 was found to be 8410 m/s., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

Exciton-light coupling in spherical microcavities containing a quantum dot has been treated by means of classical electrodynamics within the non-local dielectric response model. Typical anticrossing behavior of zero dimensional exciton-polariton modes has been obtained as well as the weak coupling strong coupling threshold., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

The nuclear spin polarization tracking the electron spin polanzation of the dark exciton does not depend on external magnetic field except in the strongly depolarized region around zero applied field with a Lorentzian lineshape with width that is two orders of magnitude greater than in bulk GaAs., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

InGaAsN insertions in a GaAs matrix grown by molecular beam epitaxy (MBE) demonstrate a pronounced effect of phase separation even at relatively low indium and nitrogen concentrations. Cross-section high-resolution transmission electron microscopy (TEM) images processed using a specially developed software demonstrated an effect of nitrogen decomnon of InAs-rich regions in the structures studied. Formation of ordered structures of compositional domains has been revealed in plan-view TEM images., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

We have calculated excitonic Bloch states in a quantum well with a two-dimensional (2D) periodic potential. For the potential parameters used the two lowest states can be well described in the tight-binding approach while the higher states represent free excitons affected by the periodic potential. The redistribution of oscillator strengths for bound-like and free-like excitons with varying the period has been also analyzed., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

We report on magneto-optical studies of spin injection from a ZnMnSe/CdSe semimag- netic short-period superlattice (SL) to a non-magnetic ZnCdSe quantum well (QW). The carriers are photo-generated in the semimagnetic SL spin polarized via the effect of giant Zeeman splitting and then injected into the non-magnetic QW through a tunneling mechanism. Near 25% injection efficiency has been demonstrated at the magnetic field of 0.8 T and low temperature (1.8 K)., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

LNGaAsN has recently been proposed as a novel material for near-infrared lasers. The merits of this material are due to the strong bowing in the bandgap of the GaAs-GaN alloy system which offers the extension of the light emission range from GaAs-based structures to 1.3 micrometers and longer. At the same time the band-offsets between InGaAsN and GaAs are larger than in the conventionally used InGaAsP system which should greatly improve high temperature performance of the 1.3 micrometer lasers. The combination with the presently available GaAs/AlAs distributed Bragg reflector (DBR) technology could also lead to novel vertical cavity lasers for the long wavelength region., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

The sp(3) tight-binding method has been applied to calculate the in-plane anisontropy of optical matrix elements for indirect electron-hole radiative recombination at a type-II interface. It has been shown that in type-II heterostructures with large band off-sets the linear polarization of the photoluminescence vary in a wide range including values ^100% as a function of the tight-binding parameters characterizing the interface cations and anions. The behaviour of electron and hole quantum-confined states near the interface and their overlap has been analyzed as well., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

The theory of weak localization is presented for quasi-2D systems where several sub- bands of size quantization are occupied. The weak-localization correction to conductivity is shown to depend strongly on the level concentration ratio and intersubband scattering intensity. Specifically at the comparable level occupations and equal relaxation times the conductivity correction of the m-subband system decreases in m times when transiting from the isolated levels to the high-intensive intersubband scattering case., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

The presented paper investigated in detail the structure and intensity of resonant exciton-phonon (REP) spectra in ZnCdSe/ZnSe QW structures as functions of tunable laser energy at 8 K. We have found that in REP spectra two types of lines are presented simultaneously. The most intensive REP component correspond to Raman scattering through extended exciton states. Other less intensive REP components correspond to hot luminescence of localized excitons. Analysis of phonon modes which can be involved in formation of REP spectra in our strain QW structures has been carried out., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

We have performed a calculation of the temperature dependence of the weak-localization correction to resistance in a AlGaAs/GaAs p-type quantum well. In such systems where the spin orbit coupling by far dominates the energy dispersion, we find that the spin relaxation time becomes comparable with the estimated value of the phase coherence time at sufficiently low temperatures and low hole densities. We wish to suggest this crossover between these different relaxation times as a possible explanation of the experimentally observed 'metal-insulator' transition in two- dimensional hole systems., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

A new simple variational wave function with a few variational parameters for 2D X(+) and X(-) trions has been suggested. The function gives accurate results for the singlet and triplet state energies of X(+) and X(-) trions in the whole range of electron-to-hole mass ratio. The mass ratio range where the triplet state exists has been found and the behavior of the triplet state energy has been examined near the critical mass ratio., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

The discovenng of NDC and mobile domain due to Bloch oscillations are the more important results in study the strong field transport in SiC superlattice. The presence of unusual mobile domain creating the breakdown avalanche is evidence oscillations possibly with terra Hz frequency., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

We study the low-temperature photoluminescence (PL) of the self-assembled InAs single quantum dots (QDs) using conventional mu-PL setup to detect PL from an individual QD. We demonstrate, that at certain experimental conditions, what concerns the laser excitation energy the laser power and the sample temperature several novel lines appear in the PL spectra. The lines redshifted relative to the exciton PL line are interpreted in terms of charged exciton complexes., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

Polarized photoluminescence and reflectance spectroscopy with high spatial resolution are employed to show the different optical properties of cleaved edges with respect to internal regions of thick GaN epitaxial layers. The values of spin-orbft and crystal-field parameters are determined separately for these areas. The obtained data indicate that an absorption edge of the material within the cleaved edge regions is below the energy of emission from internal regions which can be disadvantageous for the operation of edge-emitting devices such as LED and lasers., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

Reflectivity and ellipsometry methods were applied to study optical properties of type-II ZnSe/BeTe superlattices. Natural in-plane optical anisotropy of the refractive and absorption indices has been found in the spectral range of direct excitonic transitions. The observed effects are interpreted in a model of optical anisotropy of heterostructures with no-common atom at the interfaces., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

We study two types of GaAs-based heterostructures (InAs/InGaAs quantum dots and InGaAsN quantum wells) designed for 1.3 micrometers vertical-cavity surface-emitting lasers (VCSELs) and compare different device designs. A correlation between properties of the active region and parameters of the optical microcavity required for lasing was found and investigated. The comparative analysis of the vertical-cavity surface-emitting lasers with either InAs/InGaAs quantum dots or InGaAsN quantum wells active region operating in continuous wave regime at room temperature was done. Optimization of the optical microcavity provides the internal round-trip optical loss less than 0.05%., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

Temperature dependence of photoluminescence (PL) spectra of MBE grown ZnSe/CdSe/ZnSe QWs with 0.3-1.5 ML nominal CdSe thicknesses as well as MOCVD grown double heterostructures (DHS) GaN/InGaN/GaN with In content in the range 0.004-0.06 within the temperature interval 2-300 K has been studied. Much in common has been found in the PL band temperature behavior for both systems. Depending on the concentration of the solid solution the PL band maximum position epsilon (photoluminescence(max)( T) follows either "normal" or "anomalous" (known as "S-shape") dependence. We consider both dependances in detail and argue that anomalous behavior is caused by the fractal-like structure of the islands., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

Capacitance and photocurrent spectroscopy are used to investigate a Schottky barrier structure containing a single layer of self-organized InA/ GaAs quantum dots. We show that applying a bias to the structure it is possible to change the electron occupation of the dot levels. This in turns is used for controlling the intensity of the light absorbed by the dots and proposed as a novel way for realizing optical modulators operating in the infrared (^ 1.1 micrometer) wavelength range., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

Theoretical investigation of the separate confinement single multi quantum-well DBR laser with "curved-groove" diffraction gratings (c-DBR) is presented. Our calculations show that the proposed laser design provides both spectral selectivity of conventional DBR resonator and output beam focusing in the plane of p-n-junction. A comparison of the c-DBR and the c-DFB laser designs is also presented., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

Epitaxial MnF2 films as thick as 350 nm have been grown on Si and GaP substrates. X-ray diffractometry revealed that the MnF2 films have the alpha-PbO2 type orthorhombic structure with the lattice parameters a = 0.4953 nm b = 0.5798 nm c = 0.5362 nm. It was found that the films grown on Si111 have 111(Si)\\21-BAR1-BAR(MnF2) and 21-BAR1-BAR(Si)\\ 21-BAR1-BAR(MnF2) onentations. These epitaxial relations agree with three crystallite orientations observed by AFM. Manganese fluoride films grown on SiOO1 had the same orthorhombic structure however 010(MnF2) or 1OO(mnF2) were directed along the surface normal depending on the surface morophology of the buffer layer. Optical and magnetic measurements of the MnF2 layers are underway., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

Lately a lot of papers were devoted to the investigations of laser heterostructures based on quantum dots (QDs). This interest is based on the fact that QDs provide a zero-dimensional system with 3D carrier confinement resulting in atomic-like discrete electronic eigenstates. The delta-like state density preconditions the low theshold current densities of laser diodes and higher values of T(0) compared to existing semiconductor lasers. But the threshold current density of the classical QD laser diodes based on the single layer InAs heterostructures is far from predicted values. One of the possible obstacles to achieving the low threshold current density is low internal quantum efficiency in predicted by the theory excitation level range (10-100 A/cm2). The laser diode, which was made during this work, has a threshold current 110 A/cm2. The aim of this work is to study the mechanism limiting the quantum efficiency., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

Optically detected magnetic resonance (ODMR) and level anticrossing spectroscopy was applied to study g-factors and exchange splitting of localized excitons and e-h pairs at the X(z) - Gamma crossover of the conduction band states in a GaAs/AlAs superlattice with a composition gradient. In the transition region we clearly observed disappearance of type II excitons and appearance of type I excitons. In addition "intermediate" type-II-like and type-I-like excitons were found by ODMR and LAC. Besides ODMR of excitons with a definite fine structure splitting ODMR ascribed to separately localized electrons and holes with a distribution of exchange splittings was detected., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

We report on growth as well as optical transmission electron microscopy and X-ray diffraction studies of a new type of a GaAs/GaSb heterostructure with 1 to 3 monolayer thick GaAs layers embedded within unstrained GaSb. In such structures the GaAs layer is under tensile stress in contrast to the situation in which self-organized growth of quantum dots is commonly observed. The structure emits light in the 2 micrometer wavelength range., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings