Influence of defect diffusion on the radiation resistance of the heterogeneous photoconductor CdS-PbS

It is shown that the well-known fact that the radiation resistance of CdS improves considerably when PbS is added [A. G. Rokakh, E. V. Elagina, L. P. Matasova, and N. A. Novikova, Composition to Fabricate Film Photoresistors, Author’s Certificate No. 1110351, publ. March 17, 1983] accompanied by the formation of the heterogeneous photoconductor CdS-PbS may be attributed to the gettering of radiation defects by narrow-gap phase inclusions. This gettering occurs because the radiation-stimulated diffusion is considerably more pronounced in the wide-gap CdS-PbS component compared with the narrow-gap component. A model is proposed to explain the radiation resistance of a CdS-PbS system and this is used to determine the steady-state defect concentration profile. Pis’ma Zh. Tekh. Fiz. 25, 55–60 (December 26, 1999)     

Science of defect control in semiconductors

Abstract

A review is presented of some scientific problems underlying defect control in semiconductors, focusing particularly on the interaction of extended defects with impurities. It is demonstrated that reaction between extended defects and impurities plays a very important role in defect control in semiconductors. Some special type of reaction incorporating impurity atoms, which does not occur in the matrix region of a crystal, can occur at the core region of an extended defect because of the peculiarity in the atomic structure there. Gettering of impurities by extended defects occurs as a result of such a reaction at some specific temperatures. Impurity gettering by an extended defect causes electrical and optical inhomogeneities in the region around it. Such inhomogeneity can be controlled by heat treatment of the crystal. Impurity gettering also results in the immobilisation of dislocations. With a suitable selection of the thermal circumstances to which a crystal is exposed the generation of dislocations from structural irregularities can effectively be suppressed.     

Optical excitation of surface waves and photopiezoelectric resonance in a photorefractive crystal

Resonant optical excitation of surface waves of a photorefractive crystal (BSO) was observed for the first time when a hologram was recorded by an oscillating interference pattern. The vibrations of the surface relief observed are caused by oscillation of the space charge field and the inverse piezoelectric effect. Pis’ma Zh. Tekh. Fiz. 24, 11–16 (November 26, 1998)     

Fractal characteristics of the deformation surfaces of a composite material and their correlation with the structure

An investigation was made of the deformation relief formed at the surface of a solid under active deformation, and its fractal properties were determined. A correlation was established between the fractal dimension of the surface profile and the parameters of the fine crystalline structure of the material. Pis’ma Zh. Tekh. Fiz. 25, 34–38 (January 26, 1999)     

The effect of internal reflections of the field on the parameters of a superradiant pulse

Superadiation (SR) of an inverted two-level medium, described by one-dimensional Maxwell-Bloch equations without assuming that the amplitudes of the electric field vary smoothly along the sample, is studied. It is shown that as the initial inversion density increases, a transition is observed from the so-called “lethargic” field amplification regime, characteristic for the initial stage of SR, to a regime close to the ordinary exponential law. This accelerates the process and can lead to synchronization of counterpropagating SR pulses. Estimates are obtained for the average value of the delays of the oppositely propagating pulses and for their correlation criterion, which depends strongly on the ratio of the sample length and the half-wavelength of the resonance radiation. The possibility of realizing SR under conditions of strong phase relaxation of the active medium is discussed. Pis’ma Zh. Tekh. Fiz. 25, 24–31 (October 12, 1999)     

Probing of a random phase screen by a focused spatially modulated laser beam: Deflection of interference fringes

Deflection of interference fringes in a diffraction field was investigated under conditions in which a laser beam with a regular interference structure was finely focused onto a random phase screen. It was established that the contrast of the average-intensity fringes depends analytically on the statistical parameters of the screen. Pis’ma Zh. Tekh. Fiz. 25, 56–61 (January 12, 1999)     

Superluminescence in an AlGaAsSb/InGaAsSb/AlGaAsSb double heterostructure

Intense electroluminescence is observed for the first time in a AlGaAsSb/In_0.9Ga_0.1As_0.89Sb_0.21/AlGaAsSb double heterostructure in the 3–4 μm wavelength range at T=77 K. The structure was grown on a GaSb substrate by liquid-phase epitaxy. The photon energy at the maximum of the narrow emission band with a half-width of 9–10 eV is hv=387 meV which is 60 meV greater than the band gap of the narrow-gap InGaAsSb solid solution (E _g =326 meV). This behavior is attributed to the population inversion characteristics of the active region when an external bias is applied Pis’ma Zh. Tekh. Fiz. 23, 68–74 (May 12, 1997)     

Excitation of a potentially self-oscillating state in an oscillator with delay and inertia exposed to the simultaneous action of regular and chaotic signals

An analysis is made of the possibility of inducing a potentially self-oscillating state in a bistable self-oscillating system exposed simultaneously to regular and chaotic signals, as applied to the covert transfer of information in a binary computational system. A system of nonlinear differential difference equations is derived, which describe the behavior of an oscillator with delay and inertia under the action of complex oscillations in a given time interval. It is shown numerically that even when a potentially self-oscillating state is not excited by an external regular signal, stochastic oscillations, as well as providing a masking effect, may function as an additional stimulus to transfer the system to the basin of attraction of a potentially selfoscillating attractor. Pis’ma Zh. Tekh. Fiz. 23, 66–71 (July 26, 1997)     

Model of Laser Gettering of Fast-Diffusing Impurities

A model of gettering of fast-diffusing impurities in silicon wafers has been proposed; this model makes it possible to determine efficient gettering regimes ensuring the production of high-quality silicon wafers with reproducible characteristics for using them in the technology of creation of very large-scale integrated circuits. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 3, pp. 190–192, May–June, 2005.     

Properties of a silicon surface exposed to nanosecond laser-radiation pulses

Results of the use of nanosecond laser pulses in the technology of production of very-large-scale integration circuits are presented. It is shown that, depending on the conditions of processing of silicon by these pulses, they can avoid mechanical failure of the silicon crystal lattice and form a gettering layer that cleans the silicon from impurities. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 3, pp. 592–595, May–June, 2008.     

Dislocation structures of low-angle boundaries in Nb-doped SrTiO3 bicrystals

Dislocation core structures in low-angle boundaries of Nb-doped SrTiO₃ bicrystals were investigated by high-resolution electron microscopy. Bicrystals with tilt angles of 2°, 4°, 6° and 8° with respect to the [001] zone axis were prepared by joining two single crystals at 1873 K. All of the boundaries consisted of a regular array of dislocations whose spacing gradually decreased with an increase in tilt angle. Except for the 2° tilt-angle boundary, the dislocation cores exhibited a dissociation from a[010] into two partials of a/2[010] on (100). Furthermore, two kinds of dislocation core structures were observed; Sr–Sr atomic columns and Ti–O atomic columns inside the cores. In addition, it was found that the positioning of adjacent cores along the boundary tended to change from a linear form to a zig-zagg shape as the tilt angle was increased from 4° to 8°. In the case of the linear array, dislocation core structures including Sr–Sr columns or Ti–O columns alternately appear. In contrast, only one core structure was observed in the zig-zagged array. On the other hand, the dislocation cores in the 2°-tilt-angle boundary had another type of dissociation with a/2[110] or a/2[111] partials, which included the twist component at a tilt axis of [001].     

Gettering of iron in silicon by boron implantation

In this work we studied, both experimentally and theoretically the iron gettering by boron implantation. Sample material was p-type bulk silicon with resistivity of 21 Ωcm. Samples were iron contaminated and boron was implanted into the wafers using two different implantation doses of 4 × 10¹⁵ and 8 × 10¹⁵ cm^?2. After that various gettering annealings were performed. The results indicate that gettering cannot be explained by electronic interactions between interstitial iron and boron ions alone i.e. segregation gettering to heavily doped implantation region. It was found out that better agreement between experimental and simulation results is achieved if heterogeneous precipitation of iron to ion implantation induced damage is included in the simulations. Finally, the effects of high boron doping and gettering site morphology on iron precipitation are discussed.     

Fiber-optic detector using a mid-infrared diode laser and an acoustooptic modulator

Data are given for an infrared detector based on a semiconductor injection laser, which operates at a wavelength of 3.3 μm and is coupled by a chalcogenide optical fiber to an acoustooptic modulator made from an amorphous Si-Te alloy. The beam modulation coefficient reaches 70% for a pulse duration ≳0.3 μs, making the detector well suited to gas-analysis applications. Pis’ma Zh. Tekh. Fiz. 23, 14–18 (October 26, 1997)     

Dry etching of aluminum nitride by an ion beam

A comparative study of the important problem of dry etching AlN by an ion beam has been carried out. The etching rate as a function of the parameters of the process has been determined for layers deposited by vapor-phase epitaxy and by magnetron sputtering. It is shown possible to form a specified relief (systems of mesa stripes) in AlN layers. It is demonstrated that this method can be used for smoothing the AlN surface. Pis’ma Zh. Tekh. Fiz. 23, 1–6 (June 26, 1997)     

On evaluation of hypersingular integrals over smooth surfaces

A novel derivation is given of the decomposition of a hypersingular integral over the boundary S of a smooth 3D body into a one-dimensional integral and a regular integral over S. S is parameterized by a map q(θ,) of the unit sphere, with q(0,) at the collocation point. The integrand for the normal derivative of the field from a double-layer density is expanded in powers of a function of θ, and the distance z from S. The singularities are contained in the initial terms and give rise to the one-dimensional integral in the limit . The remainder is regular, in the limit equal to the hypersingular integrand with θ ⁻² and θ ⁻¹ terms removed. The decomposition is used to solve a standard and a hypersingular BIE for acoustic scattering, by identical high-order discretizations. Estimates of the error of the two solutions are computed to verify that their convergence rates are equal.     

Hydrogen-pellet injector using a screw extruder

The first injector design capable of injecting an unlimited supply of fuel pellets into a fusion reactor plasma in prolonged, continuous operation is reported. More than a thousand pellets 2 mm in diameter are formed without interruption from the screw extruder at frequencies of 1 Hz and 2 Hz and are accelerated to 0.8 km/s. Pis’ma Zh. Tekh. Fiz. 23, 43–46 (October 26, 1997)     

Emission of a surface acoustic wave by an internal acoustic wave propagating near the surface

It was observed that the propagation of an internal acoustic wave near a surface is accompanied by the excitation of a surface acoustic wave directed at an angle to the internal wave. Pis’ma Zh. Tekh. Fiz. 24, 57–61 (September 26, 1998)     

Characterization of novel active area silicon avalanche photodiodes operating in the geiger mode

Abstract

We present a method for characterizing avalanche photodiode (APD) photon-counting detector efficiency as a function of active area. Various shallow-junction silicon APDs having a novel active area were manufactured and tested. We show that cylindrical and checkquerboard-shaped active areas have dark counts two orders of magnitude lower than standard circular devices with an equivalent active area. A parallel implementation of small active areas creates gettering sites for defects to migrate to, which is believed to create relatively defect-free active areas as the perimeter-to-area ratio is increased. However, a compromise between a large perimeter-to-area ratio and a structure useful for practical applications must be considered to optimize the detector.     

Deep diffusion doping of macroporous silicon

An investigation is made of the diffusion of boron and phosphorus impurities in macroporous silicon with a regular structure of deep cylindrical pores, for which through doping of the walls was achieved. The ∼150 μm layers obtained were quasiuniformly doped and had a planar diffusion front, and their electric parameters were very similar to those of the doped single crystal. It is demonstrated that deep diffusion of phosphorus may be used to fabricate n-n ⁺ structures. Pis’ma Zh. Tekh. Fiz. 25, 72–79 (December 12, 1999)