Irradiation of 4<Emphasis Type="Italic">H</Emphasis>-SiC UV detectors with heavy ions

Ultraviolet (UV) photodetectors based on Schottky barriers to 4H-SiC are formed on lightly doped n-type epitaxial layers grown by the chemical vapor deposition method on commercial substrates. The diode structures are irradiated at 25°C by 167-MeV Xe ions with a mass of 131 amu at a fluence of 6 × 10⁹ cm^?2. Comparative studies of the optical and electrical properties of as-grown and irradiated structures with Schottky barriers are carried out in the temperature range 23–180°C. The specific features of changes in the photosensitivity and electrical characteristics of the detector structures are accounted for by the capture of photogenerated carriers into traps formed due to fluctuations of the conduction-band bottom and valence-band top, with subsequent thermal dissociation.     

Heavy metals (Pb,Cu, Zn and Cd) in the system soil – grapevine – grape

An Erratum has been published for this article in Journal of the Science of Food and Agriculture 79(15)1999, 2122. The investigation was carried out in the period 1991–1995 in a region with a major industrial pollutant, the Non‐Ferrous‐Metal Works, and a region with no industrial pollutants (as a control). The heavy metal content in soil, roots, annual shoots and perennial parts of grapevine, leaves, grapes and wine, was determined. Soil samples and roots of the rootstock Kober 5BB were taken at 10 cm intervals from depths of 0–100 cm. Roots were divided by thickness in fractions at 1 mm intervals. The shoots, bark, vascular tissue, wood, core and diaphragm were investigated. The leaf analyses included leaf blade and leaf petioles, and those of grapes, berry‐free raceme (washed in a lot of water and unwashed). Berries were analysed (the berry skin, the pulp and the seeds). The results obtained for the Pb, Cu, Zn and Cd contents in the grapevine roots show that they depend significantly both on their amounts in the soil and the age of the roots. The main parts of the heavy metal amounts taken by the roots of the grapevine from the soil are fixed and accumulated in the young feed rootlets (with diameters of 1 mm), and small amounts of them move through the conducting system to the older, larger diameter root system. The experimental data obtained for the presence of Pb, Cu, Zn and Cd in the separate tissues and organs of grapevines grown in an industrially polluted region showed that their amounts were mainly due to the heavy‐metal‐containing aerosols falling from the atmosphere. Part of them, however, got into the soil, and from there, even if in minimal amounts, penetrated via the root system into the grapevine plants and accumulated into their different overground parts. © 1999 Society of Chemical Industry     

Silicon carbide detectors of high-energy particles

The results of studying 4H-SiC p ⁺-n junctions ion-implanted with aluminum as detectors of high-energy particles are reported. The junctions were formed in SiC epitaxial films grown by chemical vapor deposition. The concentration of uncompensated donors was (3–5)×10¹⁵ cm⁻³, and the charge-carrier diffusion length was L _p=2.5 μm. The detectors were irradiated with 4.8–5.5-MeV alpha particles at 20°C. The efficiency of collection of the induced charge was as high as 0.35. The possibilities of operating SiC detectors at elevated temperatures (∼500°C) are analyzed. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 36, No. 6, 2002, pp. 750–753. Original Russian Text Copyright ? 2002 by Violina, Kalinina, Kholujanov, Kossov, Yafaev, Hallén, Konstantinov.     

Photoelectric properties of p +-n junctions based on 4H-SiC ion-implanted with aluminum

The photoelectric properties of p ⁺-n junctions that were based on 4H-SiC ion-implanted with aluminum and were formed in lightly doped n-type epitaxial layers grown by chemical vapor deposition were studied. It is shown that such photodetectors combine in full measure the advantages of photostructures formed on the basis of Schottky barriers and epitaxial p-n junctions. The results of the theoretical calculation of spectral characteristics of ion-implanted photodetectors are in good agreement with experimental data. The structures feature an efficiency of collection of nonequilibrium charge carriers close to 100% in the spectral range of the photon energies of 3.5–4.25 eV.     

Proton Irradiation of 4H-SiC Photodetectors with Schottky Barriers

Semiconductors - For the first time, comprehensive comparative investigations of ultraviolet photodetectors with Cr Schottky barriers formed on 4H-SiC epitaxial layers are carried out by the X-ray...     

A high-temperature radiation-resistant rectifier based on p<Superscript>+</Superscript>-n junctions in 4H-SiC ion-implanted with aluminum

A combination of a high-dose (5 s- 10¹⁶ cm^-2) implantation of Al ions into epitaxial n-type 4H SiC layers grown by chemical deposition from th e vapor phase and rapid (15 s) thermal annealing at 1700–1750°C has been used to form layers with a rectangular impurity profile according to the mechanism of solid-phase epitaxial crystallization. The combined effects of enhanced diffusion of radiation defects after implantation and gettering of defects during annealing bring about an improvement in the quality of the initial material, which ensures an increase in the diffusion length of the minority charge carriers by several times. Metastable states annealed within different temperature ranges are formed in SiC under the effect of irradiation with various particles. Low-temperature annealing of radiation defects increases the radiation and temporal lifetime of devices under irradiation. High-temperature annealing of radiation defects makes it possible to vary the lifetime of nonequilibrium charge carriers, i.e, vary the frequency range of devices. The radiation resistance of SiC-based devices increases as the operation temperature is increased to 500°C.     

Quantum efficiency of 4H-SiC detectors within the range of 114–400 nm

Technical Physics Letters - Electrical and spectrometric characteristics of 4H-SiC detectors with Cr Schottky barriers in the spectral ranges of 114–175 and 210–400 nm are studied. It...     

The challenges of virtual partnerships: Critical success factors in the formation of inter-organisational teams

Virtual teams formed across organisational boundaries and organised around an opportunity are a relatively new area of research. A review of previous research shows that, although virtual teams have been well defined as a concept, only a few studies have contributed to the understanding of the processes of assembling and maintaining effective inter-organisational teams enabled by new modes of communication. By combining cross-disciplinary theoretical approaches, the reported study presents a conceptual overview for collective teaming in virtual settings. The findings of the study confirm that inter-organisational teams follow special development patterns, which can be described as cyclical self-energising processes.     

Spectrometry of short-range ions using detectors based on 4<Emphasis Type="Italic">H</Emphasis>-SiC films grown by chemical vapor deposition

Schottky barriers, 10^?2 cm² in area, have been prepared by thermal deposition of Cr in vacuum on 50-μm-thick 4H-SiC epitaxial layers grown by chemical vapor deposition. The uncompensated donor concentration in these films is (4–6) × 10¹⁴ cm^?3, which makes it possible to extend the depletion region of the detector to ≈30 μm by applying a reverse bias of 400 V. The spectrometric characteristics of the detectors are determined using α particles in the energy range 4.8–7.7 MeV. The energy resolution attained for the 5.0-to 5.5-MeV lines is higher than 20 keV (0.34%), which, by a factor of 2, is second only to precision silicon detectors fabricated by specialized technology. The maximum signal amplitude corresponds, in SiC, to a mean electron-hole pair creation energy of 7.70 eV.     

Effect of Temperature on the Characteristics of 4H-SiC UV Photodetectors

Semiconductors - The influence exerted by the carrier concentration in the range (1–50) × 1014 cm–3 in n-4H-SiC chemical-vapor deposited (CVD) epitaxial layers on the spectral...