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

$A$ transistor is a/an

In a $P$-type semiconductor, the acceptor energy level $E_A$ is located $57 \, meV$ above the valence band. The maximum wavelength required to create a hole is ....... $\mathring{A}$. (Given: $h = 6.6 \times 10^{-34} \, J \, s$, $c = 3 \times 10^8 \, m/s$, $1 \, eV = 1.6 \times 10^{-19} \, J$)

$A$ silicon specimen is made into a $p$-type semiconductor by doping,on an average,one indium atom per $5 \times 10^7$ silicon atoms. If the number density of atoms in the silicon specimen is $5 \times 10^{28} \text{ atoms } m^{-3}$,then the number of acceptor atoms in silicon per cubic centimeter will be:

The most commonly used material for making transistors is

$A$ semiconductor doped with a donor impurity is