$A$ positive hole in a semiconductor is

Pure $Si$ at $500\, K$ has equal number of electron $(n_e)$ and hole $(n_h)$ concentrations of $1.5 \times 10^{16} \, m^{-3}$. Doping by indium increases $n_h$ to $4.5 \times 10^{22} \, m^{-3}$. The doped semiconductor is of:

In Germanium,the concentration of Aluminum is $\sim 10^{21} \text{ atoms}/m^3$. The intrinsic carrier concentration in the pure semiconductor is $\sim 10^{19} /m^3$. After adding the impurity,what is the electron concentration?

Suppose a pure $Si$ crystal has $5 \times 10^{28}$ atoms $m^{-3}$. It is doped by $1$ ppm concentration of pentavalent $As$. Calculate the number of holes. Given that $n_i = 1.5 \times 10^{16} m^{-3}$.

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

In a pure silicon, the number of electrons and holes per unit volume is $1.6 \times 10^{16} \,m^{-3}$. If silicon is doped with Boron in a way that the hole density increases to $4 \times 10^{22} \,m^{-3}$, then the electron density in the doped semiconductor will be: