Semiconductors: Feynman's Physics Explained

Feynman Vol III11-12

Energy bands explain insulators, conductors, and semiconductors. In an insulator, a band is completely full and a big gap separates it from the next empty one. In a metal, a band is only partly full, so electrons slide easily into nearby empty states and carry current. A semiconductor is an insulator with a tiny gap: at room temperature a few electrons jump across, leaving behind 'holes,' and both the electrons and the holes carry current. This is the basis of all modern electronics.

The big idea

The size of an energy gap decides if a material is wire, glass, or chip.

Think about it

Why does warming a semiconductor make it conduct better, the opposite of what happens to a metal wire?

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