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2. A Six Moments Model for the Boltzmann Equation

In this chapter we introduce the Boltzmann
transport equation (BTE) which
is the fundamental relationship
describing transport of free carriers in semiconductors.
We discuss the solution of the Boltzmann
equation by the method of moments. The arising hierarchy of
equations is simplified assuming the diffusion approximation.
Truncation of the hierarchy at a finite order
leads to a closure problem.
Closure in the scattering operator is achieved by
using the macroscopic relaxation time approximation.
Models for mobilities and relaxation times consistent with
bulk data are introduced.
Discussion of the closure in the highest order moment
is treated in Chapter 3.

**Subsections**
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**Up:** II. Nanoscale CMOS Simulation
** Next:** 2.1 The Boltzmann Poisson

R. Kosik: Numerical Challenges on the Road to NanoTCAD