How is a sample of an n-type semiconductor electrically neutral though it has an excess of negative charge carriers?
In a sample of N-type semiconductor, the number of conduction electrons is high compared to the number of holes. But the semiconductor material is electrically neutral. This is because, the charge of excess electrons are just equal and opposite to the charge of ionized immobile cores of the lattice. In a n-type there are more free negative carriers than postive ones but the amount of total negative and positive carriers is the same.