Doping of intrinsic semiconductor is done:

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

The density of an electron-hole pair in a pure germanium is $3 \times 10^{16} \ m^{-3}$ at room temperature. On doping with aluminium,the hole density increases to $4.5 \times 10^{22} \ m^{-3}$. Now,the electron density (in $m^{-3}$) in doped germanium is:

Which one of the following statements is false?

Silicon is a semiconductor. If a small amount of $As$ is added to it,then its electrical conductivity . . . . . . .

In $N$-type semiconductors,the majority charge carriers are