-\section{Band structure: indirect band gap of silicon}
-Some facts about silicon:
-\begin{itemize}
- \item Lattice constant: $a=5.43 \times 10^{-10} \, m$.
- \item Silicon has an indirect band gap.
- \begin{itemize}
- \item The minimum of the conduction band is located at
- $k=0.85 \frac{2 \pi}{a}$.
- \item The maximum of the valance band is located at $k=0$.
- \item The energy gap is $E_g=1.12 \, eV$.
- \end{itemize}
-\end{itemize}
-\begin{enumerate}
- \item Calculate the wavelength of the light necessary to lift an electron from
- the valence to the conduction band.
- What is the momentum of such a photon?
- \item Calculate the phonon momentum necessary for the transition.
- Compare the momentum values of phonon and photon.
-\end{enumerate}
-
-\section{Phonons}