On a Method of Treating Polar-Optical Phonons in Real Space

Polar-optical phonon interactions with carriers in semiconductors are long range interactions due to their Coulombic nature. Generally, if one wants to treat these with non-equilibrium Green's functions, this long-range interaction requires two- and three-particle Green's functions to be evaluated by e.g. the Bethe-Salpeter equation. On the other hand, optical phonon scattering is thought to be phase-breaking, which, if true, would eliminate this concern over long-range interactions. In seeking to determine just to what extent phase breaking is important, one could treat the polar modes as a real space potential, as is done for impurities, and examine the occurrence of any such correlations. This latter approach suffers from the condition that it is not really known how to handle the polar modes in real space -- no one seems to have done it. Here, such an approach is described as one possible method.Comment: 7 pages, 2 figur

Using Ensemble Monte Carlo Methods to Evaluate Non-Equilibrium Green's Functions, II. Polar-Optical Phonons

In semi-classical transport, it has become common practice over the past few decades to use ensemble Monte Carlo (EMC) methods for the simulation of transport in semiconductor devices. This method utilizes particles while still addressing the full physics within the device, leaving the computational difficulties to the computer. More recently, the study of quantum mechanical effects within the devices, have become important, and have been addressed in semiconductor devices using non-equilibrium Green's functions (NEGF). In using NEGF, one faces considerable computational difficulties. Recently, a particle approach to NEGF has been proposed [ 1], and preliminary results presented for non-polar optical phonons, which are very localized scattering centers. Here, the problems with long-range polar-optical phonons are discussed and results of the particle-based simulation presented.Comment: 9 pages, 9 figure

Using Ensemble Monte Carlo Methods to Evaluate Non-Equilibrium Green's Functions

The use of ensemble Monte Carlo (EMC) methods for the simulation of transport in semiconductor devices has become extensive over the past few decades. This method allows for simulation utilizing particles while addressing the full physics within the device, leaving the computational difficulties to the computer. More recently, the study of quantum mechanical effects within the devices, effects which also strongly affect the carrier transport itself, have become important. While particles have continued to be useful in quantum simulations using Wigner functions, interest in analytical solutions based upon the non-equilibrium Green's functions (NEGF) have become of greater interest in device simulation. While NEGF has been adopted by many commercial semiconductor, there remains considerable computational difficulty in this approach. Here, a particle approach to NEGF is discussed, and preliminary results presented illustrating the computational efficiency that remains with the use of particles. This approach adopts the natural basis functions for use in a high electric field and the preliminary results are obtained for quantum transport in Si at 300 K. This approach appears to offer significant advantages for the use of NEGF.Comment: 12 pages, 8 figure

Noise and Bell's inequality

From the beginning of quantum mechanics, there has been a discussion about the concept of reality, as exemplified by the EPR paradox. To many, the idea of the paradox and the possibility of local hidden variables was dismissed by the Bell inequality. Yet, there remains considerable evidence that this inequality can be violated even by classical systems, so that experiments showing quantum behavior and the violation of the inequality must be questioned. Here, we demonstrate that classical optical polarization experiments based upon noise in the system can be shown to violate the Bell inequality.Comment: Fluctuation and Noise Letters, in pres

2D Monte Carlo Simulation of Hole and Electron Transport in Strained Si

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Quantum Transport Simulation of the DOS function, Self-Consistent Fields and Mobility in MOS Inversion Layers

We describe a simulation of the self-consistent fields and mobility in (100) Si-inversion layers for arbitrary inversion charge densities and temperatures. A nonequilibrium Green's functions formalism is employed for the state broadening and conductivity. The subband structure of the inversion layer electrons is calculated self-consistently by simultaneously solving the Schrödinger, Poisson and Dyson equations. The self-energy contributions from the various scattering mechanisms are calculated within the self-consistent Born approximation. Screening is treated within RPA. Simulation results suggest that the proposed theoretical model gives mobilities which are in excellent agreement with the experimental data

Ferroelectric-Domain-Patterning-Controlled Schottky Junction State in Monolayer MoS\u3csub\u3e2\u3c/sub\u3e

We exploit scanning-probe-controlled domain patterning in a ferroelectric top layer to induce nonvolatile modulation of the conduction characteristic of monolayer MoS2 between a transistor and a junction state. In the presence of a domain wall, MoS2 exhibits rectified I-V characteristics that are well described by the thermionic emission model. The induced Schottky barrier height ΦeffB varies from 0.38 to 0.57 eV and is tunable by a SiO2 global back gate, while the tuning range of ΦeffB depends sensitively on the conduction-band-tail trapping states. Our work points to a new route to achieving programmable functionalities in van der Waals materials and sheds light on the critical performance limiting factors in these hybrid systems