When the conductivity of a semiconductor is only due to breaking of covalent bonds, the semiconductor is called

The electron concentration in an $n$-type semiconductor is the same as the hole concentration in a $p$-type semiconductor. An external electric field is applied across each of them. Compare the currents in them.

Out of the following impurities, which impurity is not a trivalent?

The conductivity of a pure semiconductor can be increased by

$A$ pure silicon crystal at temperature $300 \text{ K}$ has electron and hole concentration $(n_i) = 10^{16} \text{ per m}^3$ each. If $10^{21}$ phosphorus atoms $(n_D)$ are added per cubic metre, what is the new hole concentration in the silicon crystal?

In a $P$-type semiconductor, the acceptor level is $57 \text{ meV}$ above the valence band. What is the maximum wavelength of light (in $\mathring{A}$) required to create a hole?