$P$-type semiconductors are made by adding which impurity element?

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 $nm$)

In an $n$-type semiconductor,the free electrons donated by the impurity atoms occupy energy levels in:

The mobility of free electrons is greater than that of free holes because

In pure silicon at $300 \ K$ temperature,the concentration of electrons $n_e$ and holes $n_h$ is $1.5 \times 10^{16} \ m^{-3}$. By doping with Indium,$n_h$ is increased to $4.5 \times 10^{22} \ m^{-3}$. Calculate the concentration of electrons $n_e$ in the doped silicon.

Pure silicon at $300 \ K$ has equal electron and hole concentration of $1.5 \times 10^{16} \ m^{-3}$. If the hole concentration increases to $3 \times 10^{22} \ m^{-3}$,then the electron concentration in the silicon is