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In this paper an asymptotic solution of the spherical harmonics equations describing the charge transport in semiconductors is found. This solution is compared with a numerical solution for bulk silicon device. We also indicate application of this solution to the construction of high field hydrodynamical models.

A discretization technique is proposed for the multi‐dimensional, steady‐state hydrodynamic model of semiconductor devices, and a derivation of the model's appropriate boundary conditions is given. The model includes the complete balance equations for charge, momentum and energy, coupled with Poisson's equation, thus accounting for both diffusion and convection phenomena. The technique, like the Scharfetter—Gummel scheme for the simpler drift‐diffusion model, provides an efficient method for solving the hydrodynamic equations, allowing for a more detailed investigation of carrier dynamics in semiconductor devices.

A numerical implementation of a discretization scheme of the hydrodynamic model for submicron devices is described and applied to a one‐dimensional ballistic diode. The performance of the numerical method and the physical results of the simulation for different biases and lattice temperatures, and a brief comparison to Monte Carlo simulations, are also given.

A widely used approach for solving the two‐dimensional semiconductor‐device equations through the Finite‐Element method employs a linear approximation of the electric and quasi‐Fermi potentials over a triangular mesh; this approach combines the flexibility of FE method with the simplicity of a piecewise linear representation of the unknowns. Owing to the strong dependence of carrier densities on the position, a careful evaluation of integrals involving these quantities is desirable; this problem arises, for example, when the very common Galerkin's or Ritz's method are used, and is differently treated in the Literature. In this paper it is demonstrated that, if a minor approximation on the intrinsic carrier density is done, an analytical evaluation of the above integrals over each triangular element can be performed, which takes into account the correct dependence of carrier densities on the electric and quasi‐Fermi potentials; the results may be used to avoid heavy mesh refinements, which make the solution procedure costly both in CPU time and in memory storage. Practical applications to some specific devices will be shown elsewhere; the procedure and the final formulas are presented here in a rather general way, thus allowing a possible application to different problems which may be solved with FE method.

Some results concerning the well‐posedness of the hydrodynamic model of semiconductor devices in two dimensions are given. We show the non‐ellipticity of the stationary model; give representations which exhibit its elliptic and hyperbolic components, and obtain some appropriate boundary conditions from an examination of the time‐dependent problem.

We propose a modified discretization for the current continuity equation in the hydromodel for semiconductors. It combines ease of implementation within existing codes and robustness, even for extremely short devices. Some computational results for one and two dimensional structures are given.

We discuss the device applications of a new impact ionization model. This model is based on a new formulation of the impact ionization rate for bulk semiconductors, derived from solvable high‐field Boltzmann transport equations. The model inputs are relaxation times which simulate the dominant electron‐phonon scatterings and are calibrated by realistic Monte Carlo simulations. Our impact ionization model is shown to be physically motivated and is easily implemented in the standard hydrodynamic device simulators HFIELDS and FIELDAY. An efficient numerical scheme is used to simulate three thin‐base silicon bipolar transistors. Results based on this impact ionization model are found to agree well with the experimental multiplication factors over a large range of applied voltages. These results are contrasted with the more phenomenological treatment of Scholl and Quade which is shown to be a low‐field limit of our model.

The effects of viscosity, previously neglected in electronic device stimulations, are studied using a non‐standard hydrodynamic model, following Anile and Pennisi. Results are compared with those of Gardner.

An energy transport model has been numerically implemented in the device simulator HFIELDS. The transport parameters for the standard hydrodynamic model and the energy transport model are calibrated by means of DAMOCLES, a two‐dimensional Monte Carlo Boltzmann equation solver. We analyse the relative merits of these two models by comparing their predictions of the energy and velocity distributions for a bipolar transistor and a ballistic diode. In the cases presented, the hydrodynamic model is found to agree with the Monte Carlo results more closely than the energy transport model.

The sensory quality and yield of mozzarella cheese deteriorate as the fat content in milk is reduced. This study aims to evaluate the efficacy of sodium alginate as a fat replacer in low-fat buffalo mozzarella cheese on the basis of processing and storage (4 ± 1°C) quality.

Five treatments of buffalo mozzarella cheese, viz., control full-fat cheese (6.0 per cent milk fat; CFFC), control low-fat cheese (<0.5 per cent milk fat) without sodium alginate (CLFC), low-fat cheese with 0.1 per cent sodium alginate (LFC-1), 0.2 per cent sodium alginate (LFC-2) and 0.3 per cent sodium alginate (LFC-3), were comparatively evaluated.

Increase in the level of sodium alginate increased the percent yield of treated low-fat cheese than CLFC. Addition of sodium alginate to low-fat cheese resulted in decrease in hardness (p = 0.023) and chewiness than CLFC. Meltability was significantly decreased (p = 0.03) in low-fat cheese than CFFC. It was recorded as 1.5 ± 0.14 cm for CFFC to 0.2 ± 0.08 cm in LFC-3. Sensory panellists awarded LFC-3 highest and lowest to LFC-1; however, treated products at all selected levels were superior to CLFC. Oxidative stability and microbial stability were improved in LFC-3 than CFFC during storage.

Results concluded that 0.3 per cent sodium alginate is optimum for the development of extended shelf-life functional/low-fat/low-calorie buffalo mozzarella cheese.

Processing interventions can be successfully used to develop low-fat/low-calorie mozzarella cheese with acceptable sensory attributes and longer storage life.