If the ratio of electron and hole currents in a semiconductor is $\frac{7}{4}$ and the ratio of drift velocities of electrons and holes is $\frac{5}{4}$, then the ratio of concentrations of electrons and holes will be

The $n-$type semiconductors are obtained when germanium is doped with

In an extrinsic semiconductor,the number densities of holes and electrons are ${N_p}$ and ${N_e}$ respectively. Then:

The number of silicon atoms per $m^3$ is $5 \times 10^{28}$. This is doped with $4.5 \times 10^{21}$ atoms $/ m^3$ of Arsenic. The ratio of the number of electrons to the number of holes after doping is (Take $n_i = 1.5 \times 10^{16} / m^3$)

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: $h = 6.6 \times 10^{-34} \, J \, s$, $c = 3 \times 10^8 \, m/s$, $1 \, eV = 1.6 \times 10^{-19} \, J$)

Which of the statements given is true for a $p$-type semiconductor?