Plasma Concentration Distribution Research Articles

Математичне моделювання дифузійно-дрейфового процесу в активній області p-i-nдіодів з врахуванням розігріву та рекомбінації методами теорії збурень

With prolonged transmission of an electric current through the semiconductor devices, in a particular p-i-n diodes, an electron-hole plasma of their active region is heated. This paper presents the theoretical studies results of the plasma heating effect by the Joule heat release in the p-i-n diode volume and the charge carriers recombination energy release on the plasma concentration distribution in the p-i-n diodes active region. The mathematical model is proposed for predicting the electron-hole plasma stationary concentration distribution and the temperature field in the i-region of the bulk p-i-n diodes in the form of a nonlinear boundary value problem in a given area for the equations system, which consist of the charge carrier current continuity equations, the Poisson and the thermal conductivity. It is shown that the differential equations of the model contain a small parameter in such a way that the Poisson equation is singularly perturbed and the heat conduction equation is regularly perturbed. An approximate solution of the problem posed is obtained in the form of the corresponding asymptotic series in powers of the small parameter. The asymptotic serieses, which describes the behavior of the plasma concentration and potential in the investigated region, containing near-boundary corrections to ensure the fulfillment of the boundary conditions. The terms of these series are found as a result of solving a sequence of boundary value problems, obtained as a result of splitting the original problem, for systems of linear differential equations. The boundary value problem for a nonlinear heat equation is reduced to a sequence of problems for the corresponding linear inhomogeneous equations. The process of refining solutions is iterative. The stabilization of the process is ensured by the existence of negative feedback in the system (as the temperature rises, the mobility of charge carriers decreases).

Радиальное распределение концентрации плазмы в положительном столбе тлеющего разряда с пылевыми частицами

Радиальное распределение концентрации плазмы в положительном столбе тлеющего разряда с пылевыми частицами

The collision frequency model of the solid state plasma for Si/Si 1−x Ge x /Si SPiN device

Abstract A two dimensional(2D) collision frequency model is developed based on the 2D solid state plasma concentration distribution model and mobility model for a heterogeneous Si/Si 1−x Ge x /Si structure SPiN(Surface PiN) devices, which are the basic radiating elements in the reconfigurable solid state plasma antenna. The lower collision frequency can be achieved when the Ge mole fraction x and applied voltage increase at the temperature T=300 K, and that the basically uniform distribution of collision frequency can be obtained for Ge mole fraction x=0.3. Moreover, radiation efficiency and the maximum gain of the antenna for the different collision frequency have also been studied. The proposed model can be a handful for the designing of the solid state plasma antenna.

Simulation of hard X-ray time delays in solar flares

Hard X-ray radiation (HXR) time delays have been studied. HXR was recorded during solar flares using the BATSE spectrometer. Time-delay energy spectra were obtained for 82 flares; thе spectra were classified under three species: decreasing spectra, increasing spectra and U-shaped ones with increasing quantum energy.The spectra were derived from HXR integral over the active region. They were interpreted on the basis of a model of kinetics of accelerated electrons propagating in the flaring loop with the given plasma concentration distribution and magnetic field configuration. The kinetics in question is governed by the processes of Coulomb scattering, reflecting in the converging magnetic field, and with the return current factored in. Solving the time-dependent relativistic Fokker–Planck equation for the given initial conditions allowed to find the time-dependent electron distribution function along the loop. The brightness distribution of the bremsstrahlung of HXR derived from the electron distribution functions was calculated for different quantum energies along the flaring loop and used to plot the time-delays spectra. The calculated data showed that decreasing time-delay spectra were tractable assuming regions of electrons acceleration and injection were separated. The distinction between time-delays spectra from the looptop and footpoints was established. Hence the measurements with high resolving power may produce comprehensive data on the processes of electron transport and acceleration during solar flares.

Analytic models for solid state plasma of Si/Ge/Si heterogeneous and lateral SPiN diode

Silicon-based reconfigurable antenna, which is fabricated by heterogeneous and lateral surface PiN (SPiN), is an effective technology to achieve antenna miniaturization and enhance radar and wireless communication system performance. In this paper, the heterogeneous and lateral Si/Ge/Si SPiN diode is presented, that can weaken the band gap narrowing of the P + and N + region to improve the injection ratio of PN junction. And the electrical properties of the solid state plasma within the intrinsic region are also studied. Based on the bipolar diffusion model and Fletcher boundary condition, the analytic models of the junction voltage, the current density and the solid state plasma concentration distribution are established for a large injection current, and the numerical simulation has been carried out. Results show that the junction voltage increases linearly with the increase of applied voltage and the solid state plasma concentration at the boundary; and the current density increases exponentially with increasing junction voltage and the applied voltage, respectively. And the applied voltage and the current density of heterogeneous SPiN diode is lower than that of homogeneous SPiN diode under the same condition due to the difference of barrier heights between the heterojunction and homojunction. In addition, results also show that the value of the concentration decreases with increasing length of the intrinsic region; otherwise, it increases with increasing applied voltage and the doping concentration in the P+ and N+ regions. Under the same conditions, the solid state plasma concentration of the heterogeneous SPiN diode is nearly seven times that of homogeneous diode, which is in excellent agreement with the data published, giving the evidence for the validity of our method. The proposed models provide an effective reference for the design and application of silicon-based reconfigurable antennas.

The hydrodynamic theory of a positive discharge column in an axial magnetic field

The influence of an axial magnetic field on the performance of a low-pressure cylindrical positive discharge column is studied from the hydrodynamic point of view. It is shown that the magnetic field affects the distribution of the plasma density, its speed, and the energy of electrons. The energy of electrons, the concentration and the speed of plasma, and the azimuth speed of electrons and ions as functions of the radius have been found for a helium atom in a magnetic field of varying intensity. It has been noticed that the electron and ion azimuth movement equations should account for inertia. The obtained hydrodynamic results significantly deviate from the ones obtained in the wide-spread diffusion model of a positive column. It is shown that the distribution of plasma concentration and the radial speed in the positive column are generally close to the results using the diffusion approach, if the axial inductance of the magnetic field and the gas density are increased. However, major differences are found near the walls.

Evaluation of log-transformation in assessing bioequivalence

The question of whether we should use log-transformed data in assessing bioequivalence between two formulations is studied through a simulation. Under a 2×2 cross-over design with different combinations of sample size and intrasubject variability, we examine the impacts of different scales of the data on the conclusion of bioequivalence as well as on the level of significance and power. We also investigate the distributions of AUC and Cmax when the joint distribution of plasma concentrations is either multivariate normal or lognormal. A comparison between population bioequivalence of average bioavailability and individual bioequivalence under a lognormal distribution is also given.