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Verified Commit ba83f056 authored by Simon Josef Thür's avatar Simon Josef Thür
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\section{Fundamentals of semiconductor physics}
\section{Basics of semiconductor physics}
\subsection{Notation}
We only care about free electrons and define
\begin{equation}
\begin{split}
n &= \text{electron concentrations density}\ [cm^{-3}]\\
p &= \text{hole concentrations density}\ [cm^{-3}]\\
\end{split}
\end{equation}
\subsection{Band gap}
If an electron energy $E$ is large enough to overcome the bandgap $E_g$,
it can escape the valence band into the conduction band.
It then leaves behind a hole.
\begin{figure}[h]
\centering
\includegraphics[width=.6\textwidth]{imgs/band_gap_electorn_holes.png}
\end{figure}
\subsection{Generation and recombination}
Generation is the breakup of covalent bonds,
which creates free electrons and holes.
This requires energy, either thermal or optical.
Assuming the atom density far larger than n or p (and thus bonds can be split defacto infinitely),
we have:
\begin{align}
G & = G_{th} + G_{opt} \\
R & \sim n\cdot p
\end{align}
In thermal equilibrium, the generation and recombination rates are equal:
\begin{align}
G_0 & = f(T)=R_0 \\
\Rightarrow n_0p_0 & =n_i^2(T)
\end{align}
\subsection{Doping}
Doners are in the 5th shell (V), usually As,P,Sb.
Acceptors are in the 3rd shell (III), usually B,Al,Ga,In.
For doners we have:
\begin{align}
n_0 & = N_d \\
p_0 & = \frac{n_i^2}{N_d}
\end{align}
\subsection{Charge neutrality}
Every semiconductor is neutral,
which imposes the following condition:
\begin{equation}
P_0-n_0+N_d + N_a = 0
\end{equation}
where $p_0n_0=n_i^2$.
\ No newline at end of file
\section{Carrier transport}
\ No newline at end of file
......@@ -50,3 +50,7 @@
\rhead{\today}
\lhead{}
\cfoot{\thepage}
\numberwithin{equation}{subsection}
imgs/band_gap_electorn_holes.png

363 KiB

......@@ -32,5 +32,6 @@
\tableofcontents
\include{01_fundamentals}
\include{02_carrier_transport.tex}
\end{document}
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