How is n-type and p-type formed?

Answer 1

When in intrinsic semiconductor (pure silicon) addition of small amount of impurity of group V elements (arsenic, antimony, phosphorous) makes N-type semiconductor. V group elements provides one extra electron to silicon atom. so this makes negative charge and majority of electrons. so its called N-type..

And in P-type when in pure silicon addition of small amount of impurity of group III elements (boron, aluminum) makes the P-type. by adding IIIrd group elements they they accepts the electrons from the silicon atom since its trivalent elements so there will be vacancy of 1 electron in silicon lattice resulting the formation of "hole". This makes semiconductor positive charged semiconductor called P-type.