Electric conduction in a semiconductor takes place due to

In an $n$-type semiconductor,electrons are majority charge carriers and holes are minority charge carriers. The charge of an $n$-type semiconductor is

Which of the following statements is $\underline{TRUE}$ for $n$-type semiconductor?

Which type of impurity is to be added to a pure semiconductor to get a $p$-type semiconductor?

The most commonly used material for making transistors is

In pure silicon,the electron-hole concentration at $T = 300 \ K$ is $7 \times 10^{15} \ m^{-3}$. Antimony is added as an impurity to silicon at a rate of $1$ atom per $10^7 \ Si$ atoms. Assume that half of the impurity atoms contribute their electrons to the conduction band. Calculate the factor by which the number of charge carriers increases. Given: the number density of silicon atoms is $5 \times 10^{28} \ m^{-3}$.