S. V. Belov

Optical and electrical properties of porous silicon and stain-etched films

Abstract Photoluminescence (PL) spectra of porous silicon (PS) at 77–440 K have been studied. We report the observation of additional peaks on the PL band and pronounced fine structure at rather high temperature (77 K). We have found the transformation of the spectra when as-prepared green-emitting PS was subjected to drying in ambient air. The temperature quenching of the PL intensity revealed the same activation energy as the electroconductivity, ~ 0.3 eV, and is considered to be the ionization energy of the radiative centre. Optical absorption measurements reveal the Urbach-like behaviour of the fundamental absorption edge and the energy gap, the latter being ~ 2.4 eV.

Radiation hardness of n-GaN schottky diodes

Schottky-barrier diodes with a diameter of ~10 µm are fabricated on n-GaN epitaxial films grown by hydride vapor-phase epitaxy (HVPE) on sapphire substrates. The changes in the parameters of the diodes under irradiation with 15 MeV protons are studied. The carrier removal rate was found to be 130–145 cm–1. The linear nature of the dependence N = f(D) (N is the carrier concentration, and D, the irradiation dose) shows that compensation of the material is associated with transitions of electrons from shallow donors to deep acceptor levels which are related to primary radiation defects.

Conductivity compensation in p-6H-SiC in irradiation with 8-MeV protons

Carrier removal rate (Vd) in p-6H-SiC in its irradiation with 8-MeV protons has been studied. The p-6H-SiC samples were produced by sublimation in vacuum. Vd was determined by analysis of capacitance-voltage characteristics and from results of Hall effect measurements. It was found that complete compensation of samples with initial value of Na − Nd ≈ 1.5 × 1018 cm−3 occurs at an irradiation dose of ∼1.1 × 1016 cm−2. In this case, the carrier removal rate was ∼130 cm−1.

Effects of irradiation with 8-MeV protons on n -3 C -SiC heteroepitaxial layers

The effects of 8-MeV proton irradiation on n-3C-SiC epitaxial layers grown by sublimation on semi-insulating 4H-SiC substrates are studied. Changes in the sample parameters were recorded by the Hall-effect method and judged from photoluminescence spectra. The Hall method was employed to distinguish between the effects of irradiation on the charge-carrier concentration and mobility. It is found that the charge-carrier removal rate (Vd) is ~110 cm–1. Full compensation of the samples with an initial charge-carrier concentration of ~6.5 × 1017 cm–3 is observed at irradiation doses of ~6 × 1015 cm–2. It is found that the mobility at these doses decreased by only a factor of 2.5. Compared with 4H and 6H silicon carbide, no significant increase in the intensity of so-called defect-related photoluminescence is observed.

15 eV Protons Irradiation of the GaN Schottky Diodes

Schottky-barrier diodes with a diameter of ~10 μm are fabricated on n-GaN epitaxial films grown by hydride vapor-phase epitaxy (HVPE) on sapphire substrates. The changes in the parameters of the diodes under irradiation with 15 MeV protons are studied. The carrier rate was found to be 130-145 cm-1. The linear nature of the dependence N = F (D) (N is carrier concentration, and D, the irradiation dose) shows that compensation of the material is associated with transition of electrons from shallow donors to deep acceptor levels which are related to primary radiation defects.

P-6H-SiC Conductivity Compensation after Irradiation of 8MeV Protons

Carrier removal rate (Vd) in p-6H-SiC in its irradiation with 8 MeV protons has been studied. p-6H-SiC samples were produced by sublimation in a vacuum. Vd was determined by analysis of capacitance-voltage characteristics and from results of Hall effect measurements. It was found that full compensation of samples with initial value of Na-Nd 1.5 x1018 cm-3 occurs at an irradiation dose of ~1.1 1016 cm-2. In this case, the carrier removal rate was ~130 cm-1

“Carbonatites and Kimberlites of the World” Database and Geoinformation System: Experience of Creation and Use for Solving Geological Tasks

The article gives an overview of experience of the information database creation about the “Carbonatites and kimberlites of the World” and use of GIS technology. On this basis, the tendencies of ultrabasic alkaline massifs evolution with rare metal carbonatites, diamondiferous kimberlites and also criteria of prognostic estimations for rare metal and diamond deposits are revealed. As a whole, from older to younger epochs mineragenic evolution had the following image: (Nb→TR→P→Fe). Carbonatites are located mainly along the axis or active margins of such rift zones—“hot lines”. On the contrary, the largest manifestation of the kimberlite massifs is at a great distance from the rift zones. All these investigations became the basis for the new prospecting strategy in Russia and can be used in different regions of the World.