Irradiation with Argon Ions of Cr/4H-SiC Photodetectors

Semiconductors - The results of the effect of irradiation with Ar ions on the structural, electrophysical, and optical characteristics of ultraviolet Cr/4H-SiC photodetectors in the spectral range...     

Spin-peierls transition in the random impurity sublattice of a semiconductor

A study of electron spin resonance in uncompensated Ge:As semiconductor samples in the vicinity of the insulator-metal second-order phase transiti on reveals that the interaction of spins localized at As atoms brings about a distortion of the crystal lattice and enhances the localization. This effect occurs in the range of electron concentrations n = 3 × 10¹⁷—3.7 × 10¹⁷ cm^-3, just below the critical point of the phase transition. The effect is explained in the context of a model considering the spin-Peierls transition in the random impurity sublattice of the semiconductor, and its features, as compared to other known materials where the spin-Peierls transition is observed, are understood.     

Electron spin resonance in the vicinity of metal-insulator transition in compensated n-Ge:As

Electron spin resonance (ESR) is investigated in the vicinity of metal-insulator transition in compensated n-Ge:As. It is found that the 10-GHz signal is observed from both sides of the transition up to a temperature of 100 K. ESR spectrum in metallic samples looks like a single line of the Dyson type, with the line shape varying with temperature. The Dyson line in the insulating samples transforms into the Lorentz line which splits into two lines at temperatures below 4.1 K. One line has an ordinary shape, the other has an anomalous step-like shape in the magnetic field, increasing with decreasing temperature. This effect has not been satisfactorily explained so far. Two mechanisms are proposed for the spin relaxation observed, one of which is related to donor-acceptor pairs and the other, to phonons. The Pauli and Curie paramagnetism is found in metallic and insulator samples, respectively.     

Microwave magnetoresistance of compensated p-Ge:Ga in the region of the insulator-metal phase transition

The microwave magnetoresistance (MR) of neutron transmutation doped (moderately compensated) Ge:Ga in the insulator-metal transition region was studied using ESR technique. As the hole concentration increases, the MR mechanism changes in the insulator state near the phase transition point: the hopping conductivity that is characterized by the impurity wave-function contraction by the magnetic field is replaced by the state of weak localization. In the latter case, the temperature dependence of the diffusion coefficient is of great importance near the transition point (1.2×10¹⁷ cm^?3). This dependence decreases in the metallic state. In the metallic state, the diffusion coefficient is independent of temperature and the MR temperature dependence is described by the dephasing mechanism due to phonon scattering. The electron-electron interaction contribution to the dephasing time should be considered for heavier doping.     

Estimating the Ratio of Composite Ingredients by the Two-Energy Transmission Method

The possibility of measuring the ratio of composite ingredients using the two-energy transmission method has been studied. This technique differs from the known methods by its independence from the specific weight of the tested object. An equation of a measuring instrument with correction for the methodological error is derived. The formulas relating the error in concentration estimates to the errors in the calibration coefficients are presented.__________Translated from Defektoskopiya, Vol. 41, No. 4, 2005, pp. 70–75.Original Russian Text Copyright © 2005 by Zabrodskii, Nedavnii, Osipov.     

Injection-induced terahertz electroluminescence from silicon <Emphasis Type="Italic">p–n</Emphasis> structures

Injection-induced terahertz electroluminescence from silicon p ⁺–n structures is observed at helium temperatures. Structures fabricated by the diffusion of boron into a phosphorus-doped n-Si substrate are studied. Relatively narrow luminescence lines are observed in the luminescence spectra against a broad smooth background. The spectral position of a number of emission lines corresponds to optical transitions between excited donor states and the ground state of phosphorus donors. The intracenter optical transitions of electrons at phosphorus donors are excited as a result of recombination processes occurring in the n-type region of the structure under the injection of nonequilibrium holes. A number of other lines in the terahertz emission spectra are associated with intracenter transitions at acceptor centers, which are also excited as a result of injection. The structureless background in the electroluminescence spectra may be due to terahertz emission upon the intraband energy relaxation of “hot” carriers having an effective temperature exceeding the lattice temperature. These “hot” carriers appear in the structure under injection conditions.     

Radiative heat transfer in a charge of disperse material

An equation for calculating the energy flux created by thermal radiation in disperse charges is derived. The equation describes a one-dimensional process, and correlates well with experimental data.     

Determination of 90Sr, 238Pu, 239,240Pu, 241Pu, and 241Am in soils of chernobyl region using various sample preparation techniques

Radiochemical analysis is made of soddy-podzolic sandy and peaty gley soils collected from the Chernobyl zone. Radionuclides were separated by extraction chromatography or ion exchange, and then determined using an α-ray spectrometer and liquid scintillation and proportional gas counters. Leaching from the preliminarily calcined sample with 8 M HNO₃ does not ensure 100% recovery of radionuclides from peaty gley soil.     

Silicon Light-Emitting Diodes with Luminescence from (113) Defects

Semiconductors - Silicon light-emitting diodes with luminescence associated with (113) defects are fabricated by the implantation of 350-keV oxygen ions at a dose of 3.7 × 1014 cm–2 and...