Why for making an n-type semiconductor silicon or germanium is doped with only fifteenth group element like phosphorus?

Answer 1

in silicon or germanium, the valence shell contain 4 electrons. in order to attain stability,

they need 4 more electrons, so we doping it either with trivalent or pentavalent

impurities. if we are doping semiconductor with any of these, we call it as an extrinsic

semiconductor if we are using pentavalent impurity such as phosphorous, there will be an

extra electron,which will go to conduction band. we know electron has negative charge

therefore we call it as n-type semiconductor

Answer 2

N-type semiconductors like silicon or germanium are doped with group 15 elements like phosphorus because they have 5 valence electrons, one more than the atoms in the crystal lattice. This extra electron becomes a free electron when the atom bonds with the semiconductor lattice, increasing the conductivity of the material.