If a semiconductor has an intrinsic carrier concentration of $1.41 \times 10^{16} \, m^{-3}$,when doped with $10^{21} \, m^{-3}$ phosphorus,then the concentration of holes at room temperature will be

At room temperature,a $p$-type semiconductor has

The net charge on an $N-$type semiconductor is

Suppose an $n$-type wafer is created by doping $Si$ crystal having $5 \times 10^{28} \text{ atoms/m}^3$ with $1 \text{ ppm}$ concentration of $As$. On the surface,$200 \text{ ppm}$ Boron is added to create a $p$-region in this wafer. Considering $n_i = 1.5 \times 10^{16} \text{ m}^{-3}$,$(i)$ Calculate the densities of the charge carriers in the $n$ and $p$ regions. $(ii)$ Comment on which charge carriers would contribute largely to the reverse saturation current when the diode is reverse biased.

In $P$-type semiconductors,the majority and minority charge carriers are respectively:

Why is it required to add impurity to a pure semiconductor? Mention its condition and explain what impure semiconductors are.