Lecture 12: Semiconductors

Today is all about semiconductors. We talk about how to dope them. Donor atoms "donate" electrons into the conduction band, giving n-type semiconductors, with mostly electrons carrying current. Acceptor atoms "accept" atoms from the valence band, leaveng holes there. These are p-type semiconductors. We also discuss the effective mass of the electrons and holes in a band, and how to calculate it. (It changes based on the curvature of the band -- that's right, the electron might act more or less free inside the material, but act as though it has a different mass.) We look at the physics of how the dopant atoms "ionize" to contribute carriers to the semiconductor.
There's also a way to measure whether the semiconductor's main carriers are holes or electrons, using the Hall Effect.

Lecture Audio