SIMON is a single electron tunnel device and circuit simulator that is based on a Monte Carlo method. It allows transient and stationary simulation of arbitrary circuits consisting of tunnel junctions, capacitors, and voltage sources of three kinds: constant, piecewise linearly time dependent, and voltage controlled. Cotunneling can be simulated either with a plain Monte Carlo method or with a combination of the Monte Carlo and master equation approach. A graphic user interface allows the quick and easy design of circuits with single-electron tunnel devices. Furthermore, as an example of the usage of SIMON, we discuss the essential problem of random background charge and present possible solutions.

Since Stratton published his famous paper four decades ago, various transport models have been proposed which account for the average carrier energy or temperature in one way or another. The need for such transport models arose because the traditionally used drift-diffusion model cannot capture nonlocal effects which gained increasing importance in modern miniaturized semiconductor devices. In the derivation of these models from Boltzmann's transport equation, several assumptions have to be made in order to obtain a tractable equation set. Although these assumptions may differ significantly, the resulting final models show various similarities, which has frequently led to confusion. We give a detailed review on this subject, highlighting the differences and similarities between the models, and we shed some light on the critical issues associated with higher order transport models.

We describe a user-oriented software tool-MINIMOS-for the two-dimensional numerical simulation of planar MOS transistors. The fundamental semiconductor equations are solved with sophisticated programming techniques to allow very low computer costs. The program is able to calculate the doping profiles from the technological parameters specified by the user. A new mobility model has been implemented which takes into account the dependence on the impurity concentration, electric field, temperature, and especially the distance to the Si-SiO2interface. The power of the program is shown by calculating the two-dimensional internal behavior of three MOST's with 1-µm gate length differing in respect to the ion-implantation steps. In this way, the threshold voltage shift by a shallow implantation and the suppression of punchthrough by a deep implantation are demonstrated. By calculating the output characteristics without and with mobility reduction, the essential influence of this effect is shown. From the subthreshold characteristics, the suppression of short-channel effects by ion implantation becomes apparent. The MINIMOS program is available for everyone for just the handling costs.

A model capturing the effect of general strain on the electron effective masses and band-edge energies of the lowest conduction band of silicon is developed. Analytical expressions for the effective mass change induced by shear strain and valley shifts/splittings are derived using a degenerate kldrp theory at the zone-boundary X point. Good agreement to numerical band- structure calculations using the nonlocal empirical pseudopotential method with spin-orbit interactions is observed. The model is validated by calculating the bulk electron mobility under general strain with a Monte Carlo technique using the full-band structure and the proposed analytical model for the band structure. Finally, the impact of strain on the inversion-layer mobility of electrons is discussed.

Small semiconductor devices can be separated into regions where the electron transport has classical character, neighboring with regions where the transport requires a quantum description. The classical transport picture is associated with Boltzmann-like particles that evolve in the phase-space defined by the wave vector and real space coordinates. The evolution consists of consecutive processes of drift over Newton trajectories and scattering by phonons. In the quantum regions, a convenient description of the transport is given by the Wigner-function formalism. The latter retains most of the basic classical notions, particularly, the concepts for phase-space and distribution function, which provide the physical averages. In this work we show that the analogy between classical and Wigner transport pictures can be even closer. A particle model is associated with the Wigner-quantum transport. Particles are associated with a sign and thus become positive and negative. The sign is the only property of the particles related to the quantum information. All other aspects of their behavior resemble Boltzmann-like particles. The sign is taken into account in the evaluation of the physical averages. The sign has a physical meaning because positive and negative particles that meet in the phase space annihilate one another. The Wigner and Boltzmann transport pictures are explained in a unified way by the processes drift, scattering, generation, and recombination of positive and negative particles. The model ensures a seamless transition between the classical and quantum regions. A stochastic method is derived and applied to simulation of resonant-tunneling diodes. Our analysis shows that the method is useful if the physical quantities do not vary over several orders of magnitude inside a device.