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Verified Commit 1834093c authored by Simon Josef Thür's avatar Simon Josef Thür
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add 1st part of chap 2

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\section{Carrier transport} \section{Carrier transport}
\ No newline at end of file \subsection{Fermi distribution}
\label{label:sec:fermi}
Fermions are weird particles, see QM II.
Not sure if needed for this course, but heres the probability distribution:
\begin{equation}
f(E) = \frac{1}{1+e^{(E-E_F)/kT}}
\end{equation}
Electron concentration in conductance band:
\begin{equation}
n=N_ce^{-(E_c-E_f)/kT}
\end{equation}
Hole concentration in valence band:
\begin{equation}
p=N_ve^{-(E_f-E_v)/kT}
\end{equation}
In intrinsic silicon ($n=p=n_i$) we have ($E_i$ somewhere in the middle of the bandgap)
\begin{equation}
E_i=E_f=\frac{E_c+E_v}{2}-\frac{kT}{q}\ln{\frac{N_c}{N_v}}
\end{equation}
Which gives us the useful relation:
\begin{equation}
n_i = \sqrt{N_cN_v}e^{-(E_c-E_v)/2kT} = \sqrt{N_cN_v}e^{-E_g/2kT}
\end{equation}
\subsubsection{Temperature dependance}
Looking at the equations in \autoref{label:sec:fermi} we see that the higher the temperature or the lower the band-gap, the more electrons and holes are created.
\subsection{Carrier transport}
\subsubsection{Thermal equilibrium}
\begin{align}
\lambda & \equiv \text{mean free path} [cm] \\
\tau_c & \equiv \text{mean time between collisions} [s^{-1}] \\
v_{th} & \equiv \text{thermal velocity} [cm/s] \\[1em]
\lambda & = v_{th}\cdot\tau_c
\end{align}
\subsubsection{Drift velocity}
Quick electromag recap: (for holes use + and $m_p$)
\begin{align}
F & = -qE \\
v(t) & =-\frac{qE}{m_n}t
\end{align}
Average drift velocity:
\begin{equation}
v_d = \pm \frac{qE\tau_c}{2m_{n,p}}
\end{equation}
\subsubsection{Mobility}
\begin{align}
\mu_{n,p} & = \frac{q\tau_c}{2m_{n,p}} \equiv \text{mobility}\ [cm^2/Vs] \\
amhere
\end{align}
\ No newline at end of file
...@@ -32,6 +32,6 @@ ...@@ -32,6 +32,6 @@
\tableofcontents \tableofcontents
\include{01_fundamentals} \include{01_fundamentals}
\include{02_carrier_transport.tex} \include{02_carrier_transport}
\end{document} \end{document}
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