What is a semiconductor?

A material whose ability to conduct electricity sits between a conductor and an insulator — and can be controlled.

What you’ll learn

The defining property of a semiconductor
Common semiconductor materials
Why controllable conductivity matters

Why it matters

Every chip exists because a semiconductor's conductivity can be tuned by doping, voltage, light, or temperature.

Explanation

A semiconductor is a material with electrical conductivity between that of a conductor (like copper) and an insulator (like glass). Silicon is the dominant example; germanium and compound semiconductors such as gallium arsenide (GaAs) and gallium nitride (GaN) are also used.

The crucial feature is not the middling conductivity itself but that it can be controlled precisely — by adding tiny amounts of impurities (doping) or by applying an electric field. That controllability is what makes switches, amplifiers, and logic possible.

Visual explanation

A conductivity scale: insulators (glass) on the left, metals (copper) on the right, and semiconductors (silicon) in the tunable middle band.

Key terminology

Conductivity: How easily a material carries electric current.
Silicon: The most widely used semiconductor element.
Compound semiconductor: A semiconductor made of two or more elements (e.g. GaAs).

Example

Pure silicon barely conducts, but adding one boron atom per million silicon atoms makes it conduct far better — a change you engineer on purpose.

Common mistakes

Watch out for:

Thinking semiconductors are simply 'weak conductors' — the point is that the conductivity is controllable.
Assuming silicon is the only semiconductor; compound semiconductors dominate optoelectronics and power.

Real-world application

Silicon underpins essentially all logic and memory chips; GaN and SiC are rising in power electronics.

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