$A$ semiconductor doped with a donor impurity is

The valence of the impurity atom that is to be added to a germanium crystal to make it an $N$-type semiconductor is:

An $n$-type and a $p$-type silicon semiconductor can be obtained by doping pure silicon with

In a semiconductor,the number densities of electrons and holes are $8 \times 10^{18} \ m^{-3}$ and $5 \times 10^{18} \ m^{-3}$ respectively. If the mobilities of electrons and holes are $2.3 \ m^2/V \cdot s$ and $0.01 \ m^2/V \cdot s$ respectively,then the semiconductor is:

$A$ semiconductor has equal electron and hole concentration of $2 \times 10^8 \ m^{-3}$. On doping with a certain impurity, the electron concentration increases to $4 \times 10^{10} \ m^{-3}$. What is the new hole concentration of the semiconductor?

Which of the following statements is true for an $N$-type semiconductor?