\chapter{Introduction}

Silicon carbide (SiC) has a number of remarkable physical and chemical properties that make it a promising new material in various fields of applications.
The high electron mobility and saturation drift velocity as well as the high band gap and breakdown field in conjunction with its unique thermal stability and conductivity unveil SiC as the ideal candidate for high-power, high-frequency and high-temperature electronic and optoelectronic devices exceeding conventional silicon based solutions \cite{wesch96,morkoc94,casady96,capano97,pensl93}.
Due to the large Si--C bonding energy SiC is a hard and chemical inert material suitable for applications under extreme conditions and capable for microelectromechanical systems (MEMS), both as structural material and as a coating layer \cite{sarro00,park98}.
Its radiation hardness allows the operation as a first wall material in nuclear reactors \cite{giancarli98} and as electronic devices in space \cite{capano97}.


The realization of silicon carbide based applications demands for reasonable sized wafers of high crystalline quality.
Despite the tremendous progress achieved in the fabrication of high purity SiC employing techniques like the modified Lely process for bulk crystal growth \cite{tairov78,tsvetkov98} or chemical vapour deposition (CVD) and molecular beam epitaxy (MBE) for homo- and heteroepitaxial growth \cite{}, available wafer dimensions and crystal qualities are not yet considered sufficient enough.

New means: Ion beam synthesis (IBS) of burried SiC layers ...
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Model of precipitation ...
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Therefore the understanding of carbon, as an isovalent impurity in silicon is of fundamental interest...
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Control of dopant diffusion in silicon device manufacturing / transient enhanced diffusion (TED) ...
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Strained silicon to achieve higher charge carrier velocities ...
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In chapter ...


