Intrinsic semiconductor

A pure, undoped semiconductor where electrons and holes come only from thermal generation.

What you’ll learn

What 'intrinsic' means
Electron–hole pair generation
Why intrinsic material is rarely used directly

Why it matters

Intrinsic behaviour is the baseline you modify by doping to build real devices.

Explanation

In an intrinsic (pure) semiconductor, the only carriers come from thermal energy knocking electrons from the valence to the conduction band. Each promoted electron leaves a hole, so electrons and holes are equal in number (n = p = ni).

This intrinsic carrier concentration is tiny and strongly temperature-dependent, so pure silicon is a poor conductor. Real devices deliberately add impurities to fix the carrier type and concentration.

Visual explanation

Equal numbers of free electrons (–) and holes (+) scattered through a pure silicon lattice.

Key terminology

Intrinsic carrier concentration (ni): Carrier density in pure material.
Electron–hole pair: An electron and the hole it leaves behind.
Hole: A missing valence electron that acts like a positive carrier.

Formula

n = p = ni

In intrinsic material, electron and hole concentrations are equal.

Example

Silicon's ni is about 10^10 per cm³ at room temperature — vanishingly small next to ~10^22 atoms per cm³.

Common mistakes

Watch out for:

Thinking pure silicon is a good conductor — it barely conducts.
Forgetting holes contribute to current alongside electrons.

Real-world application

Wafers start close to intrinsic and are doped region-by-region to build transistors.

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