Extrinsic Semiconductor - n-type semiconductor

• The semiconductor in which a silicon or germanium crystal is doped with a pentavalent impurity (donor), making electrons the majority charge carriers, is called an n-type semiconductor.
• When a few atoms of the pentavalent elements (phosphorus, arsenic, antimony and bismuth) are added to the pure germanium or silicon crystal, the resulting crystal is called an n-type semiconductor.

The pentavalent impurity atom added during doping in an n-type semiconductor is known as a donor.

• An n-type semiconductor is formed by doping with a pentavalent impurity (e.g., Phosphorus, Arsenic, Antimony, Bismuth).
• Arsenic has 5 outer electrons — 4 are used in bonding with silicon, and the 5th electron is free to move and conduct.
• The pentavalent impurity atom acts as a donor as it donates a free electron.
• Electrons are majority carriers; holes are minority carriers — ne≫nhne​≫nh.
• The donor energy level lies approximately 0.1 eV below the conduction band.
• The Fermi level shifts closer to the conduction band in n-type semiconductors.