The density of an electron-hole pair in a pure germanium is $3 \times 10^{16} \ m^{-3}$ at room temperature. On doping with aluminium,the hole density increases to $4.5 \times 10^{22} \ m^{-3}$. Now,the electron density (in $m^{-3}$) in doped germanium is:

In pure $Si$ at $300 \ K$,the concentration of electrons $(n_e)$ and holes $(n_h)$ is equal and is $1.5 \times 10^{16} \ m^{-3}$. If the concentration of holes $(n_h)$ increases to $3 \times 10^{22} \ m^{-3}$ after doping with Indium,calculate the concentration of electrons $(n_e)$ in the doped $Si$.

In an intrinsic semiconductor,the energy gap $E_{g}$ is $1.2 \; eV$. Its hole mobility is much smaller than electron mobility and independent of temperature. What is the ratio between conductivity at $600 \; K$ and that at $300 \; K$? Assume that the temperature dependence of intrinsic carrier concentration $n_{i}$ is given by $n_{i} = n_{0} \exp \left(-\frac{E_{g}}{2 k_{B} T}\right)$,where $n_{0}$ is a constant.

Silicon is a semiconductor. If a small amount of $As$ is added to it,then its electrical conductivity . . . . . . .

$A$ hole in a $P-$type semiconductor is

Minority carriers in a $p$-type semiconductor are