Optical properties of strain-compensated InAs/InGaAsN/GaAsN superlattices

The optical properties of heterostructures comprising InAs/InGaAsN quantum wells in strain-compensated GaAsN/InGaAsN superlattices have been studied. It is demonstrated that, using such superlattices of various design and thickness and with additional InAs monolayer spacers, it is possible to control the wavelength of room-temperature emission from InGaAsN quantum wells within 1.3–1.6 μm without deteriorating the output radiation characteristics, which opens additional prospects for the development of lasers on GaAs substrates for telecommunication applications.     

Tellurium clusters in channels of the porous silica ZSM-11

The distribution and structure of tellurium nanoclusters synthesized in crystal channels of the porous silica ZSM-11 are investigated using the maximum-entropy method and the Rietveld analysis. It is shown that the intercalated tellurium atoms are arranged in channels of the ZSM-11 zeolite not randomly but in the form of scraps of infinite chains similar to those observed in massive tellurium. The distances between the nearest neighbor tellurium atoms vary in the range 2.53(4)–2.70(3) ?. The clusters Te₄ are formed at the intersections of channels in the structure. These clusters have the form of distorted tetrahedra in which the tellurium atoms are separated by distances of 2.53(4) and 2.90(4) ?. Original Russian Text ? A.E. Lapshin, Yu.F. Shepelev, Yu.I. Smolin, E.A. Vasil’eva, 2008, published in Fizika i Khimiya Stekla.     

Radioecological state of the territory and water area in Guba Andreev

The radioecological conditions which developed on the territory over the long operating time of the object of the naval fleet in Guba Andreev are described. The results of an analysis of the sources of the real and potential danger and measures to prevent dangerous effects for the environment and the workers at the time remediation work is performed are discussed. __________ Translated from Atomnaya énergiya, Vol. 101, No. 1, pp. 49–55, July, 2006.     

Impedance spectroscopy of ultrafine-grain SnO2 ceramics with a variable grain size

The impedance spectra of nanocrystalline SnO₂ ceramics with an average grain size d ranging from 3 to 43 nm were investigated in the frequency range 1–10⁶ Hz at temperatures from 25 to 300°C in a dry oxygen atmosphere. Analysis of the experimental data by the graphoanalytical method made it possible to separate the contributions of grain bulk and grain boundaries to the conductivity. It is shown that the samples investigated can be arbitrarily divided into two groups with respect to the character of their conductivity. For the samples with an average grain size d < 25 nm, the charge transfer processes are almost completely determined by the grain boundaries. In samples with a larger grain size, the contribution of grain bulk to the conductivity is comparable with that of grain boundaries.     

Forming n-p junctions based on p-CdHgTe with low charge carrier density

The first results on the formation of n ⁺-p photodiodes with a long-wavelength boundary at λ_0.5 = 10.6 μm based on p-CdHgTe epilayers with a hole density of 3.3 × 10¹⁴ cm^?3 are presented. The CdHgTe layers were obtained by molecular beam epitaxy and exhibited p-type conduction in the as-grown state. The hole density and mobility were determined by means of the mobility spectrum technique. The photodiode structures were prepared by B⁺ ion implantation into as-grown p-CdHgTe epilayers without additional annealing. The R ₀ A product for the n ⁺-p photodiodes obtained is about 20 Θ cm² at 77 K.     

Temperature dependence of the effective coefficient of Auger recombination in 1.3 μm InAs/GaAs QD lasers

Semiconductor laser heterostructures containing five and ten sheets of InAs/GaAs QDs on GaAs substrates, with an emission wavelength of ～1.3 μm, have been studied. Dependences of the nonradiative lifetime and effective Auger coefficient in QDs are obtained from an analysis of temperature and current dependences of the efficiency of spontaneous radiative recombination. The zero-threshold Auger recombination channel in QDs is shown to dominate at low (below 200 K) temperature, whereas at higher temperatures the quasithreshold channel becomes dominant. The effective 3D Auger coefficient is estimated in the approximation of a spherical QD, and a good agreement with the experimental data is obtained.     

Terbium-doped garnet single crystals as X-ray-sensitive phosphors

The spectra of luminescence induced by synchrotron radiation in the fundamental absorption range were measured at 10 and 300 K for Czochralski-grown bulk Y₃Al₅O₁₂ single crystals doped with Tb³⁺ ions and for (Tb,La,Gd)₃Ga₅O₁₂ single crystal films grown by liquid phase epitaxy from a PbO-B₂O₃ based supercooled solution melt on Gd₃Ga₅O₁₂ substrates.     

Methods and results of tests of a large model of the TUK-84 container

Tests of a prototype model of TUK-84 and the corresponding experimental procedures used at the test center of the All-Russia Research Institute of Technical Physics are described. The results are presented, and it is shown that the prototype withstood the tests. __________ Translated from Atomnaya énergiya, Vol. 100, No. 6, pp. 441–445, June, 2006.     

Sixty Mb/s transversal equalizer

A model of a linear digital communication system is introduced and adaptive equalization in general is explained. A five-tap transversal equalizer is designed, breadboarded and tested in a 60 Mb/s burst mode modem in a quasi-linear and a non-linear channel under the following configurations:

• 1 Parabolic, linear and combination of parabolic and linear delay distortions were inserted after the non-linearity (TWTA).
• 2 Case 1 was repeated with distortions inserted before the non-linearity.

When parabolic distortion is added before the non-linearity improvements in the BER are significant.