When a semiconductor is doped with donor impurity,

Which of the following dopants is used in germanium to form an $n$-type semiconductor?

At room temperature,a $p$-type semiconductor has

In which of the following statements is the obtained impure semiconductor of $p$-type?

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 $5 \times 10^{28} \ m^{-3}$.

In a semiconductor,the concentration of electrons is $8 \times 10^{14} \text{ cm}^{-3}$ and that of the holes is $5 \times 10^{12} \text{ cm}^{-3}$. The semiconductor is