Semicond. Physics Quantum Electronics & Optoelectronics, 2014, № 4

Studies on the optical fluxes attenuation process in optoelectronic systems

Wed, 01 Jan 2014 00:00:00 GMT

Studies on the optical fluxes attenuation process in optoelectronic systems Strelkova, T.A. In this paper, the statistical characteristics of output signals in optoelectronic systems with a limited dynamic range are considered. The experimental results concerning noises probability densities are adduced. It has been shown that the law of output signal distribution depends on attenuation factor of neutral filter used for matching the dynamic range. The output signal distribution law is well approximated by the steady distributions with characterization index 0 < α < 2. Using the stable law as a limiting one allows to avoid the contradiction between experimental data and common mathematical models of signals based on the Poisson and Gaussian statistics and to reduce weak signals detection errors in optoelectronic systems with implementation of neutral filters for matching the dynamic range.

Magnetic and magnetoresistive characteristics of neutron-irradiated Si₀.₉₇Ge₀.₀₃ whiskers

Wed, 01 Jan 2014 00:00:00 GMT

Magnetic and magnetoresistive characteristics of neutron-irradiated Si₀.₉₇Ge₀.₀₃ whiskers Litovchenko, P.G.; Pavlovska, N.T.; Pavlovskyy, Yu.V.; Ugrin, Yu.O.; Luka, G.; Ostrovskyy, I.P. The effect of 8.6∙10¹⁷ n/cm² with fast neutron irradiation on the magnetic susceptibility of Si₀.₉₇Ge₀.₀₃ thread-like crystals (whiskers) with impurity concentration near metal-insulator junction has been studied. Significant differences have been observed in the change of magnetic susceptibility of irradiated whiskers and bulk Cz-Si. The low-temperature (4.2…40 K) changes of magnetoresistance in magnetic fields up to 14 T, caused by irradiation, have been studied. It has been established that at temperatures near 4.2 K, a significant contribution to the conductivity is made by light charge carriers of low concentration but with high mobility. The level supplying these charge carriers has the energy of e = 2.1 meV, and with application of magnetic field it increases up to e = 2.5 meV in approx. 10 T field. It demonstrates the fact that the reason of magnetoresistance, beside the magneto-field decrease of mobility, is the magneto-field decrease in the free carrier concentration. At temperatures approx. 40 K, conductivity is due to holes, the activation energy whereof is e = 11.5 meV, which is practically independent of the magnetic field.

Uncooled р(Pb₁₋xSnxSe)-n(CdSe) heterostructure-based photodetector for the far infrared spectral range

Wed, 01 Jan 2014 00:00:00 GMT

Uncooled р(Pb₁₋xSnxSe)-n(CdSe) heterostructure-based photodetector for the far infrared spectral range Lepikh, Ya.I.; Ivanchenko, I.A.; Budiyanskaya, L.M. The possibility to create uncooled photodetector (PD) in the region close to l = 10 μm being based on p(Pb₁₋xSnxSe)-n(CdSe) heterojunction has been conceptually and practically confirmed. Design and technology of uncooled thin-film PD based on Pb Sn Se₁₋x p -n(CdSe) heterojunction in which broad-band CdSe layer is located on the illuminated surface and plays the role of the optical filter with respect to the lower layer of ternary compound. The PD spectral characteristics at room temperature have been researched, which confirms the photoactivity of both heterojunction layers. The mechanism of current flow in the PD structure based on the above heterojunction and the mechanism of the PD samples sensitivity at room temperature in the far infrared spectrum, the determining factor of which is the amount of wide-gap semiconductors where space charge-limited current appears, have been investigated. The uncooled PD detectability typical for polycrystalline structures 106 …107 сm*Hz¹/²/W has been discovered.

Statistical structure of the biological tissue scattering of laser field with the complex degree of coherence

Wed, 01 Jan 2014 00:00:00 GMT

Statistical structure of the biological tissue scattering of laser field with the complex degree of coherence Angelsky, P.O. Diagnostic efficiency of differentiation of birefringence of rat’s biological tissues in different physiological states is studied in this research based on application of the correlation approach. Interrelation between coordinate distributions of complex degree of coherence (CDC) and changes in birefringence has been determined.