Question 5
5 pts
In general, how does the electron diffusion coefficient in a semiconductor
change with doping concentration?
$\circ$ Dn increases with increasing donor doping concentration
$\circ$ Dn does not depend on the donor doping concentration
$\circ$ Dn decreases with increasing donor doping concentration
$\circ$ Dn would only begin to increase in the degenerate doping regime
$\circ$ One cannot say in general because the dependence would be different for different
semiconductors
Question 6
5 pts
Consider an n-type Si material doped at $N_a = 10^{16}$ cm$^{-3}$ under steady-state
illumination at room temperature. If the light is absorbed uniformly leading to a
generation rate, $g = 10^{20}$ cm$^{-3}$s$^{-1}$, and the minority carrier lifetime is
$\tau_p = 1$
$\mu$s, determine the fractional change in the conductivity of the material relative
to that in the dark,
$\frac{\Delta \sigma}{\sigma}$
$\circ$ 2000%
$\circ$ 1.3%
$\circ$ 0.002%
$\circ$ 90%
The conductivity of the wafer will not change
