Intrinsic vs. Extrinsic Semiconductors: Understanding the Difference

The terms “intrinsic” and “extrinsic” describe how a semiconductor’s electrical properties are determined.

Intrinsic Semiconductors

• Pure semiconductor material (e.g., pure silicon, germanium).
• Electrical properties depend only on the material itself—band gap, temperature, crystal structure.
• At absolute zero, they act as perfect insulators; conductivity rises with temperature as electron‑hole pairs are thermally generated.
• Equal numbers of electrons and holes (n = p = nᵢ).

Extrinsic Semiconductors

• Doped with intentional impurities (dopants) to alter conductivity.
• n‑type: Donor atoms (e.g., phosphorus in Si) add free electrons (majority carriers).
• p‑type: Acceptor atoms (e.g., boron in Si) create holes (majority carriers).
• Electrical properties are strongly influenced by external factors: dopant type/concentration, temperature, and defects.
• Conductivity is orders of magnitude higher than intrinsic material at room temperature.

Why It Matters

Controlled doping creates p‑n junctions—the foundation of diodes, transistors, solar cells, and integrated circuits. Intrinsic material is rarely used alone in devices but serves as the substrate for extrinsic regions.