On the relationship between radiation-stimulated photoluminescence and nitrogen atoms in p-4H-SiC

Photoluminescence (PL) appearing in p-4H-SiC upon its electron irradiation has been studied. A model that accounts for the dependence of the PL intensity on the irradiation dose is suggested. The conclusion is drawn that nitrogen–radiation defect donor–acceptor pairs are PL activators.     

Effect of electron and proton irradiation on characteristics of SiC surface-barrier detectors of nuclear radiation

Structures with a Schottky barrier based on CVD-grown 4H-SiC films were irradiated with 8 MeV protons and 900 keV electrons. The maximum fluences were 10¹⁴ and 3 × 10¹⁶ cm^?2, respectively. It was found that, in the case of electrons, the primarily introduced radiation defects are closely spaced Frenkel pairs. Changes in the electrical characteristics of the structures were compared. Capacitance methods and nuclear spectrometry were employed. The latter technique was used to determine the charge collection efficiency under pulsed ionization with α-particles. It was determined that, under proton irradiation, the charge collection efficiency steadily decreases as the fluence increases. For electrons, the efficiency remains unchanged in the fluence range (1–3) × 10¹⁶ cm^?2. However, a fluence of 3 × 10¹⁶ cm^?2 leads to a pronounced increase in the non-uniformity of charge transport conditions throughout the sample volume.     

Low-Temperature Annealing of Lightly Doped n-4H-SiC Layers after Irradiation with Fast Electrons

Semiconductors - The effect of low-temperature (up to 600°C) isothermal and isochronous annealing on the electrical characteristics of irradiated n-4H-SiC JBS Schottky diodes is studied....     

Diversity of Properties of Device Structures Based on Group-III Nitrides,Related to Modification of the Fractal-Percolation System

A fractal-percolation system that includes extended defects and random fluctuations in the alloy composition is formed during the growth of device structures based on Group-III nitrides. It is established that the specific features of this system are determined not only by the growth conditions. It is shown that the diversity of the electrical and optical properties of InGaN/GaN LEDs (light-emitting diodes) emitting at wavelengths of 450–460 and 519–530 nm, as well as that of the electrical properties of AlGaN/GaN HEMT (high-electron-mobility transistor) structures, is due to modification of the properties of the fractal-percolation system both during the growth process and under the action of the injection current and irradiation. The influence exerted by these specific features on the service life of light-emitting devices and on the reliability of AlGaN/GaN HEMT structures is discussed.

     

Impact of High-Energy Electron Irradiation on Surge Currents in 4H-SiC JBS Schottky Diodes

Semiconductors - The effect of irradiation with high-energy (0.9 MeV) electrons on surge currents in high-voltage (operating voltage 1700 V) 4H -SiC Schottky p-n diodes is studied in the...     

Leptospirosis: its diagnostic and treatment characteristics

To close extensive infected wounds and to replace long bone defects, along with other methods a method of graded tissue strain (GTS) has been developed and introduced into practice (246 patients). The method differs from all others in that it requires no transfer of elaborate flaps while replacing soft tissue defects; and no graft or foreign body is introduced externally into the wound in replacing long bone defect. Soft tissue defect is gradually replaced by wound-adjacent intrinsic tissues, the wound is closed by related skin and bone defect is filled by an osseous regenerate which is formed during graded transposition of the osteotomized fragment. At the same time good blood supply and tissue innervation retain, which contributes to their resistance to purulent infection. The analysis of the findings has led to the conclusion that GTS is an indispensible contribution to the development of plastic purulent surgery allowing the anatomic and functional integrity of the diseased segment to be restored.     

The regulation of calcium homeostasis in nerve cells

We have reviewed the major cellular elements related to the release and buffering of calcium in neurons. Voltage-operated, chemical-operated calcium channels and mechanisms of stability of intercellular calcium homeostasis (mitochondria, endoplasmic reticulum, calcium binding proteins, calcium exchange and calcium pump) are demonstrated in normal and pathological condition (105 ref.).     

Formation of Radiation Defects by Proton Braking in Lightly Doped <Emphasis Type="Italic">n</Emphasis>- and <Emphasis Type="Italic">p</Emphasis>-SiC Layers

Mathematical simulation of the cascade of displacements in SiC is used to consider the specific features of Frenkel-pair generation upon the scattering of 8- and 15-MeV protons. The distribution histograms of energies acquired not only by primary knocked-out atoms, but also by recoil atoms generated in displacement cascades, are calculated. An analysis of the histograms considers two energy ranges. In the first range of “low” energies, the spontaneous recombination of genetically related Frenkel pairs is dominant. Recoil atoms in the second range have a higher energy, which enables these atoms to leave the spontaneousrecombination zone and dissociate into isolated components. The compensation of lightly doped n- and p-4H-SiC samples grown by gas-phase epitaxy is experimentally studied under irradiation with 8- and 15-MeV protons. The carrier removal rates are measured. The calculated and experimental data are compared and estimates are obtained for the size of the spontaneous-recombination zone.     

Effect of electron irradiation on carrier removal rate in silicon and silicon carbide with 4H modification

Comparative study of the effect of successive (up to fluences of 3 × 10¹⁶ cm^?2) irradiation with 900 keV electrons of samples made of FZ-Si and 4H-SiC (CVD) has been performed for the first time. Measurements on initial and irradiated samples were made using the van der Pauw method for silicon and the capacitance-voltage technique at a frequency of 1 kHz for silicon carbide. In addition, the spectrum of the defect levels introduced was monitored by the DLTS method for SiC. The carrier removal and defect introduction rates were determined for the two materials. It was found that the rates of defect introduction into FZ-Si and 4 H-SiC (CVD) are close to eachy other (～0.1 cm^?1), which is largely due to the almost identical threshold energies of defect generation.