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

Pure Silicon crystal at $300 \ K$ has equal electron and hole concentration of $1.5 \times 10^{16} \ m^{-3}$. Doping by indium increases $n_h = 4.5 \times 10^{22} \ m^{-3}$. The $n_e$ in the doped silicon is:

$A$ semiconductor doped with a donor impurity is

The temperature $(T)$ dependence of resistivity $(\rho)$ of a semiconductor is represented by

An $N-$type and $P-$type silicon can be obtained by doping pure silicon with

$A$ potential difference of $2.5 \,V$ is applied across the faces of a germanium crystal plate. The face area of the crystal is $1 \,cm^2$ and its thickness is $1.0 \,mm$. The free electron concentration in germanium is $2 \times 10^{19} \,m^{-3}$ and the electron and hole mobilities are $0.33 \,m^2/V \cdot s$ and $0.17 \,m^2/V \cdot s$ respectively. The current across the plate will be .......... $A$.