$A$ transistor is a/an

In a semiconductor,the intrinsic carrier concentration of electrons and holes is $6 \times 10^8 \ m^{-3}$. After doping with some impurity,the electron concentration increases to $9 \times 10^{12} \ m^{-3}$. Find the new hole concentration.

The acceptor level of a $p$-type semiconductor is $6 \ eV$ above the valence band. The maximum wavelength of light which can create a hole would be: (Given $hc = 1242 \ eV \ nm$) (in $nm$)

If a small amount of antimony is added to germanium crystal,

$A$ hole in a $P-$type semiconductor is

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