Impact ionization fronts in Si diodes: Numerical evidence of superfast propagation due to nonlocalized preionization

We present numerical evidence of a novel propagation mode for superfast impact ionization fronts in high-voltage Si $p^+$-$n$-$n^+$ structures. In nonlinear dynamics terms, this mode corresponds to a pulled front propagating into an unstable state in the regime of nonlocalized initial conditions. Before the front starts to travel, field-ehanced emission of electrons from deep-level impurities preionizes initially depleted $n$ base creating spatially nonuniform free carriers profile. Impact ionization takes place in the whole high-field region. We find two ionizing fronts that propagate in opposite directions with velocities up to 10 times higher than the saturated drift velocity.Comment: 3 pages, 4 figure

Dynamic avalanche breakdown of a p-n junction: deterministic triggering of a plane streamer front

We discuss the dynamic impact ionization breakdown of high voltage p-n junction which occurs when the electric field is increased above the threshold of avalanche impact ionization on a time scale smaller than the inverse thermogeneration rate. The avalanche-to-streamer transition characterized by generation of dense electron-hole plasma capable to screen the applied external electric field occurs in such regimes. We argue that the experimentally observed deterministic triggering of the plane streamer front at the electric field strength above the threshold of avalanche impact ionization but yet below the threshold of band-to-band tunneling is generally caused by field-enhanced ionization of deep-level centers. We suggest that the process-induced sulfur centers and native defects such as EL2, HB2, HB5 centers initiate the front in Si and GaAs structures, respectively. In deep-level free structures the plane streamer front is triggered by Zener band-to-band tunneling.Comment: 4 pages, 2 figure

Electronic structure of GaAs1-xNx alloy by soft-X-ray absorption and emission: Origin of the reduced optical efficiency

The local electronic structure of N atoms in a diluted GaAs1-xNx (x=3%) alloy, in view of applications in optoelectronics, is determined for the first time using soft-X-ray absorption (SXA) and emission (SXE). Deviations from crystalline GaN, in particular in the conduction band, are dramatic. Employing the orbital character and elemental specificity of the SXE/SXA spectroscopies, we identify a charge transfer from the N atoms at the valence band maximum, reducing the overlap with the wavefunction in conduction band minimum, as the main factor limiting the optical efficiency of GaAs1-xNx alloys. Moreover, a k-conserving process of resonant inelastic x-ray scattering involving the L1 derived valence and conduction states is discovered.Comment: 3 pages, physica status solidi (Rapid Research Notes), in pres

Polymorphism of CYP2C9 gene in patients with stable angina pectoris and its significance in pathogenesis of the disease

A study of 90 patients with stable angina pectoris was performed. The polymerase chain reaction was used to determine the gene polymorphisms of cytochrome CYP2C9*2 C430T. The condition of DNA was studied by the method of DNA comet assa

Tunneling-assisted impact ionization fronts in semiconductors

We propose a novel type of ionization front in layered semiconductor structures. The propagation is due to the interplay of band-to-band tunneling and impact ionization. Our numerical simulations show that the front can be triggered when an extremely sharp voltage ramp ($\sim 10 {\rm kV/ns}$) is applied in reverse direction to a Si $p^+-n-n^+-$structure that is connected in series with an external load. The triggering occurs after a delay of 0.7 to 0.8 ns. The maximal electrical field at the front edge exceeds $10^6 {\rm V/cm}$. The front velocity $v_f$ is 40 times faster than the saturated drift velocity $v_s$. The front passes through the $n-$base with a thickness of $100 {\mu m}$ within approximately 30 ps, filling it with dense electron-hole plasma. This passage is accompanied by a voltage drop from 8 kV to dozens of volts. In this way a voltage pulse with a ramp up to $500 {\rm kV/ns}$ can be applied to the load. The possibility to form a kilovolt pulse with such a voltage rise rate sets new frontiers in pulse power electronics.Comment: 12 pages, 6 figure

The importance of the smoking factor in personalized complex pharmacotherapy of ischemic heart disease with the use of metabolic correctors

The work is devoted to the study of the significance of the smoking factor in the realization of potentially positive cardiocytoprotective properties of metabolic correctors in the complex therapy of ischemic heart disease (IHD). A randomized study of 160 patients with stable angina pectoris was performed, 60 of them were smoking and 100 of them were non-smokin

Age-related features of the pathogenesis of ischemic heart disease and sensitivity of patients’ DNA to cytoprotectors

The high prevalence of coronary heart disease (CHD) and the increase in mortality from this nosology among patients of older age groups determine the urgency of the problem of improving the provision of medical care to this category of patients. This research is devoted to the study of the effect of cytoprotective therapy on the course of coronary artery disease in elderly patients in terms of its necessity and feasibilit

Гидрогеологические аспекты развития водохозяйственных технологий урбанизированных территорий на примере Оренбуржья

In the conditions of increasing industrial load especially in combination with arid climate, negative geodynamic processes develop on Earth, including depletion and pollution of water resources. More than 1.5 billion people suffer from the lack of water resources and the processes of pollution of natural waters. For more than two thousand years, people on the planet have been solving water management problems by building water reservoirs and the simplest water management structures. However, in arid climate, the construction of reservoirs is accompanied by the large losses of water due to evaporation. To overcome these difficulties, water management technologies are being developed. They are aimed in increasing the water reserves of water intakes based on the accumulation of a part of the floodwater.В условиях НТР и особенно засушливого климата на Земле развиваются негативные геодинамические процессы, включая истощение и загрязнение водных ресурсов. Более 1,5 млрд человек преодолевают трудности, связанные с недостатком водных ресурсов и процессами загрязнения природных вод и ОС. Уже более двух тысяч лет люди на планете решают водохозяйственные задачи путем строительства водохранилищ и простейших водохозяйственных сооружений. Однако в условиях аридного климата строительство водохранилищ сопровождается большими потерями воды на испарение. Аридизация климата затронула свыше 35% суши. В условиях НТР и широкого развития процессов техногенеза значительно возросли и продолжают расти расходы воды, усиливая истощение водных ресурсов и ухудшение их качества. Для преодоления этих трудностей развиваются водохозяйственные технологии, заключающиеся в увеличении запасов вод водозаборов за счет аккумуляции части паводковых вод

Stimulated emission of radiation using spin-population inversion in metals: a spin-laser

Arrays of 10 nm-diameter point contacts of exchange-coupled spin-majority/spin-minority ferromagnetic metals, integrated into infrared-terahertz range photon resonators, are fabricated and measured electrically and optically. Giant, threshold-type electronic excitations under high-current pumping of the devices are observed as abrupt but reversible steps in device resistance, in many cases in access of 100%, which correlate with optical emission from the devices. The results are interpreted as due to stimulated spin-flip electron-photon relaxation in the system.Comment: 5 page