What is the valency of donor impurity? Name these impurities.

Let ${n_h}$ and ${n_e}$ be the number of holes and conduction electrons respectively in a semiconductor. Then

$A$ $N-$ type semiconductor is

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:

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

In extrinsic $P$ and $N$-type semiconductor materials,the ratio of the impurity atoms to the pure semiconductor atoms is about