The resistance of intrinsic semiconductors decreases with the increase of temperature. Doping pure $Si$ with trivalent impurities gives $p-$type semiconductors. A $p-n$ junction can act as a semiconductor device.

The majority of carriers in $n-$type semiconductors are electrons, not holes. Atoms got a greater amount of electrons in the conduction band of a $n-$type semiconductor, i.e. doped with a pentavalent impurity, in comparison to the number of holes in the valence band.