Which of the following energy band diagrams shows the $N-$ type semiconductor?

The Bohr radius of the fifth electron of phosphorus (atomic number $Z = 15$) acting as a dopant in silicon (relative dielectric constant $\varepsilon_r = 12$) is ....... $\mathring{A}$.

Why are elemental dopants for Silicon or Germanium usually chosen from group $XIII$ or group $XV$?

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

The impurity atoms which are mixed with pure silicon to make a $P$-type semiconductor are those of:

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