There can be little doubt that the Monte Carlo method for semiconductor device simulation has enormous power as a research tool. It represents a detailed physical model of the semiconductor material(s), and provides a high degree of insight into the microscopic transport processes. However, if the authority ascribed to Monte Carlo models of devices at 1/spl mu/m feature size is to be maintained for devices below O.1/spl mu/m, modelling of the fundamental physics must be further improved. And if the Monte Carlo method is to be successful as a semiconductor device design tool, the device model must be made more realistic. Success in the industrial sector depends on this, but also on achieving fast run-times optimisation - where the scope and need for ingenuity is now greatest.

The Monte Carlo method for semiconductor device simulation

The extraction and combustion of fossil natural gas, consisting primarily of methane, generates vast amounts of greenhouse gases that contribute to climate change. However, as a result of recent research efforts, “solar methane” can now be produced through the photocatalytic conversion of carbon dioxide and water to methane and oxygen. This approach could play an integral role in realizing a sustainable energy economy by closing the carbon cycle and enabling the efficient storage and transportation of intermittent solar energy within the chemical bonds of methane molecules. In this article, we explore the latest research and development activities involving the light-assisted conversion of carbon dioxide to methane. While natural gas and fossil fuels power human activities, increasing concerns over fuel reserves and environmental impacts require finding alternative, renewable resources. Here, authors review the fundamental science and progress on solar-powered conversion of carbon dioxide to methane.

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Fundamentals and applications of photocatalytic CO 2 methanation

1. Introduction and preliminaries 2. Molecular orbitals-potentials-dynamics, and quantum energy states 3. Carrier energy transport and transition theories 4. Phonon energy storage, transport and transition kinetics 5. Electron energy storage, transport and transition kinetics 6. Fluid particle energy storage, transport and transformation kinetics 7. Photon energy storage, transport and transition kinetics.

Heat Transfer Physics

Comparison of different modeling approaches for thermoelectric elements

We model and evaluate the Peltier and Seebeck effects in magnetic multilayer nanostructures by a finite-element theory of thermoelectric properties. We present analytical expressions for the thermopower and the current-induced temperature changes due to Peltier cooling/heating. The thermopower of a magnetic element is in general spin polarized, leading to spin-heat coupling effects. Thermoelectric effects in spin valves depend on the relative alignment of the magnetization directions and are sensitive to spin-flip scattering as well as inelastic collisions in the normal-metal spacer.

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Thermoelectric effects in magnetic nanostructures

The thermo-emf in bipolar semiconductors is calculated. It is shown that it is necessary to take into account the nonequilibrium distribution of electron and hole concentrations (Fermi quasilevels of the electrons and holes). We find that electron and hole electric conductivities of contacts of semiconductor samples with connecting wires make a substantial contribution to thermo-emf.

Nature of the thermopower in bipolar semiconductors.

A new approach is suggested to explain the Peltier effect. It assumes that the Peltier effect is not an isothermal effect. The approach is based on the occurrences of induced thermal fluxes in a structure which consists of two conducting media, through which a dc electric current flows. These induced thermal diffusion fluxes arise to compensate for the change in the thermal flux caused by the electric current (the drift thermal flux) flowing through the junction, in accordance with the general Le Chprinciple. The occurrence of these thermal diffusion fluxes leads to temperature heterogeneity in the structure and, as a result, to a cooling or heating of the junction. Within the framework of this concept, the thermoelectric cooling is analysed. It is shown that in the general case the Peltier effect always occurs together with another thermoelectric effect. This thermoelectric effect is predicted for the first time, and we have called it the barrierless thermoelectric effect. Both these effects essentially depend on the junction surface thermal resistance. The Peltier effect disappears in the limiting case of a very large surface thermal resistance, while the barrierless effect disappears in the limiting case of a very small surface thermal resistance. The dependence of thermoelectric cooling on the geometrical dimensions of the structure is noted, and the corresponding interpretation of this fact is discussed. It is shown that the thermoelectric cooling (heating) is a thermodynamically reversible process in the linear approximation of the electric current applied.

https://iopscience.iop.org/article/10.1088/0268-1242/20/12/R01/pdf

Physics of thermoelectric cooling

In this work we present results concerning the fundamental equations of charge-carrier transport in semiconductor structures. We discuss a correct modeling of the recombination terms that does not violate the charge conservation law. We obtained that under stationary conditions and equal generation rates of electrons and holes the recombination rates of both kinds of carriers must be matched. Under low excitation conditions (linear regime) the recombination rate can be expressed as a linear combination of the excess concentrations of electrons and holes, and only in very precise situations can a lifetime be defined. Explicit calculation of the charge variation was carried out within the framework of the band-to-band and Shockley-Read-Hall statistics. It is shown that the bulk space charge established on distances of the order of Debye’s length cannot influence the current-voltage characteristics of a device in a linear regime. It was also shown that metal-p-type semiconductor contacts are essentially diff...

Transport of nonequilibrium carriers in bipolar semiconductors

A new approach is presented to thermoelectric phenomena, as a linear transport process of non-equilibrium charge carriers. The role of non-equilibrium carriers, as well as surface and bulk recombination, has shown to be crucial even within the linear approximation. Electron and hole Fermi quasi-levels that appeared in a thermal field are calculated for the case of thermoelectric current flow through a circuit and the corresponding boundary conditions are obtained. It is shown for the first time that the Fermi quasi-level of one of the subsystems of quasi-particles, can be a non-monotonous function of the coordinates. General expressions for the thermoelectric current, thermo-e.m.f., and electrical resistance of bipolar semiconductors have been obtained. For the first time, surface recombination and surface resistance were taken into account in thermoelectric phenomena.

The Role of Non‐Equilibrium Carriers in the Formation of Thermo‐E.M.F. in Bipolar Semiconductors

A new approach to thermoelectric phenomena, as a linear transport process of non-equilibrium charge carriers, is presented. The role of non-equilibrium carriers, as well as surface and bulk recombination, is demonstrated to be crucial even within a linear approximation. Electron and hole Fermi quasi-levels appeared in a thermal field are calculated in the case of thermoelectric current flow through a circuit. It is shown, for the first time, that the Fermi quasi-level of one of subsystem of quasi-particles can be a non-monotonic function of the coordinates. General expressions for the thermoelectric current, thermo-e.m.f., and electrical resistance of bipolar semiconductors have been obtained. For the first time the surface recombination and surface resistance were taken into account.

Yu. G. Gurevich

Papers

Nature of the thermopower in bipolar semiconductors.

Physics of thermoelectric cooling

Transport of nonequilibrium carriers in bipolar semiconductors

The Role of Non‐Equilibrium Carriers in the Formation of Thermo‐E.M.F. in Bipolar Semiconductors

The Role of Non-Equilibrium Carriers in Formation of Thermo-E.M.F. in Bipolar Semiconductors