The width of the forbidden gap in a silicon crystal is $1.1 \, eV$. When the crystal is converted into an $N$-type semiconductor,the distance of the Fermi level from the conduction band is:

What is an acceptor impurity? Write the names of such impurities.

The typical ionisation energy of a donor in silicon is.....$eV$

If a small amount of antimony is added to germanium crystal,

Write briefly on $n$-type and $p$-type semiconductors.

In a semiconductor,the number density of intrinsic charge carriers at $27^{\circ} \text{C}$ is $1.5 \times 10^{16} \, \text{m}^{-3}$. If the semiconductor is doped with impurity atoms,the hole density increases to $4.5 \times 10^{22} \, \text{m}^{-3}$. The electron density in the doped semiconductor is $..... \times 10^{9} \, \text{m}^{-3}$.