Suppose a pure $Si$ crystal has $5 \times 10^{28}$ atoms $m^{-3}$. It is doped with $1 \text{ ppm}$ concentration of pentavalent $As$. Calculate the number of electrons and holes. $(n_i = 1.5 \times 10^{16} \text{ m}^{-3})$

If $n_{e}$ and $n_{h}$ are concentrations of electrons and holes in a semiconductor,then the intrinsic carrier concentration $(n_i)$ in thermal equilibrium is

$A$ $P$-type semiconductor has acceptor levels $57 \; meV$ above the valence band. The maximum wavelength of light required to create a hole is (Planck's constant $h = 6.6 \times 10^{-34} \; J \cdot s$, speed of light $c = 3 \times 10^8 \; m/s$)

Mobility of electrons in a semiconductor is defined as the ratio of their drift velocity to the applied electric field. If,for an $n$-type semiconductor,the density of electrons is $10^{19} \ m^{-3}$ and their mobility is $1.6 \ m^2/(V \cdot s)$,then the resistivity of the semiconductor (since it is an $n$-type semiconductor,the contribution of holes is ignored) is close to ................ $\Omega \cdot m$.

In an $N$-type semiconductor,where are the donor energy levels $E_D$ located?

$A$ $P$-type semiconductor is .......