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Proposes a finite element method for numerical simulation of the hydrodynamic model of semiconductor devices. Presents some scaling factors and a variational formulation. Uses the P₁ ‐ isoP₂ element to discretize this formulation and the GMRES (Generalized Minimum RESidual) algorithm to solve the associated non‐linear system. Proposes an artificial viscous term to stabilize the non‐linear system. Gives a choice for an initial solution. Presents the numerical solutions for n⁺ ‐ n ‐ n⁺ diodes and 0.25μm gate length Si MESFETs. Calculates a shock wave at 300K. Observes velocity overshoot phenomenon and the effect of heat conduction term.

Electrical potentials in a junction field transistor can be calculated using a simplified model based on a complete depletion assumption. This gives rise to a free boundary problem. We show here how we can approximate this problem with a quasi‐variational inequality technique and the shape optimization method. A detailed analysis of these methods is presented. Using some numerical experiments we compare our results with the solution of the discrete drift‐diffusion system, accomplished with a Gummel‐like algorithm. The numerical results suggest that the methods proposed here work successfully and that the shape optimization technique provides a reasonably free boundary without excessive iterations.

This study aims to examine the electromigration processes resulting from thermal overloads of semiconductor devices. While in operation, parts of such devices can heat up to 330°C for a short period, resulting in the emergence of molten zones and the devices’ inevitable degradation. Therefore, this study examines the mechanisms behind the formation and migration of silver-based molten zones in bulk germanium and on its surface.

Experimental data concerning the correlation between the migration velocities of the inclusions and their sizes are obtained.

By comparing these experimental data with known electromigration models, it is concluded that inclusions move through the mechanism of melting and crystallization. The dynamics of Ge–Ag zones in the volume of a germanium crystal are compared to those on its surface and accelerated electromigration on the surface of the crystal is observed. This increased migration velocity is shown to be associated with additional contributions of the electrocapillary component.

The results of this study can be used to calculate the operating modes of semiconductor power devices under intense heat loading.

We discuss three models describing the carrier densities in highly doped silicon, which have been used for process and device simulation. We calculate nie for each of the models for various doping concentrations within temperature ranges interesting for the device and process simulation. We try to explain the behaviour of nie for high compensation and compare our calculated results to measured values of nie. We offer simple formulae for the calculated nie and show how far the relations between the carrier densities and the Fermi levels can be described by the simple formulae of Boltzmann statistics when we use a doping dependent effective intrinsic number.

The Monte‐Carlo particle model is a technique of simulating small semiconductor devices. It consists briefly of following the detailed transport histories of individual carriers, their time of free flight and consequent scattering chosen by a random number technique. A description of the method is given. The method has proved itself successful in semiconductor analysis, and as an example of its application we are using it to study the influence the epitaxial doping has on the performance of field‐effect transistors. We are comparing a transistor with an epitaxially grown active layer, with one with an ion implanted active layer and with an ideal device with an abrupt transition between the epilayer and the substrate. The cut‐off bias for ideal transistor is found to be more sharply defined than for the other two types of transistors. The spatial distribution of the carriers follows roughly the doping profile near the source. Underneath the gate the peak of the carrier density is pushed further down and into the substrate as the gate bias increases. This peak also weakens as the gate bias rises, and vanishes at, and beyond cut‐off. In the high field region after the gate the upper valleys population increases with increased drain bias and decreases with increased gate bias. The power gain and the y‐parameters are examined for all devices, both near pinch‐off and for no external gate bias. In both cases the ion implanted transistor shows the greatest gain. This transistor also exhibits the lowest minimum noise figure.

A general algorithm for analysis of semiconductors with arbitrary models for heavy doping phenomena is presented. Different models, theoretical as well as empirical, were applied, and minority carrier concentration in the uncompensated n‐type silicon was analyzed. Recalculated into the term of apparent BGN, the results were compared with experimental data. Further analysis of apparent BGN indicated the weakness of empirical formulae for apparent BGN. Assumption of total ionization of impurities considered in the analysis is discussed and justified.

This review aims to give an overview about zinc oxide (ZnO) based gas sensors and the role of doping in enhancing the gas sensing properties. Gas sensors based on ZnO thin film are preferred for sensing applications because of their modifiable surface morphology, very large surface-to-volume ratio and superior stability due to better crystallinity. The gas detection mechanism involves surface reaction, in which the adsorption of gas molecules on the ZnO thin film affects its conductivity and reduces its electrical properties. One way to enhance the gas sensing properties is by doping ZnO with other elements. A few of the common and previously used dopants include tin (Sn), nickel (Ni) and gallium (Ga).

In this brief review, previous works on doped-ZnO formaldehyde sensing devices are presented and discussed.

Most devices provided good sensing performance with low detection limits. The reported operating temperatures were within the range of 200̊C –400̊C. The performance of the gas sensors can be improved by modifying their nanostructures and/or adding dopants.

As of yet, a specific review on formaldehyde gas sensors based on ZnO metal semiconductors has not been done.

A hydrodynamic semiconductor device simulator, DYNA, is introduced. A new relaxation time evaluation scheme for two‐valley semiconductors is proposed to account for the dependence of the electron mobility on the impurity scattering. Some robust solution methods are used in the simulator for treating the highly nonlinear system of equations. The simulation results for a nonuniformly‐doped GaAs MESFET are also shown.

This paper aims to characterize the relationship between the interelectrode capacitance (C) of metal-oxide-semiconductor field-effect transistors (MOSFETs) and the applied bias voltage (V) by a fractional-order equivalent model.

A Riemann–Liouville-type fractional-order equivalent model is proposed for the C–V characteristic of MOSFETs, which is based on the mathematical relationship between fractional calculus and the semiconductor physical model for the interelectrode capacitance of metal oxide semiconductor structure. The C–V characteristic data of an N-channel MOSFET are obtained by Silvaco TCAD simulation. A differential evolution-based offline scheme is exploited for the parameter identification of the proposed model.

According to the results of theoretical analysis, mathematical derivation, simulation and comparison, this paper illustrates that, along with the variation of bias voltage applied, the interelectrode capacitance (C) of MOSFETs performs a fractional-order characteristic.

This work uncovers the fractional-order characteristic of MOSFETs’ interelectrode capacitance. By the proposed model, the influence of doping concentration on the gate leakage parasitic capacitance of MOSFETs can be revealed. In the pre-defined doping concentration range, the relative error of the proposed model is less than 5% for the description of C–V characteristics of metal-oxide-semiconductor field-effect transistors (MOSFETs). Compared to some existing models, the proposed model has advantages in both model accuracy and model complexity, and the variation of model parameters can directly reflect the relationship between the characteristics of MOSFETs and the doping concentration of materials. Accordingly, the proposed model can be used for the microcosmic mechanism analysis of MOSFETs. The results of the analysis produce evidence for the widespread existence of fractional-order characteristics in the physical world.

We present a qualitative analysis of the fundamental static semiconductor device equations which is based on singular perturbation theory. By appropriate scaling the semiconductor device equations are reformulated as singularly perturbed elliptic system (the Laplacian in Poisson's equation is multiplied by a small parameter ?2, the so‐called singular perturbation parameter). Physically the singular perturbation parameter is identified with the square of the normed minimal Debye length of the device under consideration. Using matched asymptotic expansions for small A we characterize the behaviour of the solutions locally at pn junctions, Schottky contacts and oxide‐semiconductor interfaces and demonstrate the occurrence of exponential internal/boundary layers at these surfaces. The derivatives of the solutions blow up within these layer regions (as ?2 decreases) and they remain bounded away from the layers. We demonstrate that the solutions of the ‘zero‐space charge approximation’ are close to the solutions of the ‘full’ semiconductor problem (when ? is small) away from layer regions and derive a second‐order ordinary differential equation which (when subjected to appropriate boundary/interface conditions) ‘describes’ the solutions within layer regions.