Solid State Electronic Devices, 7th Edition

3.2 Charge Carriers in Semiconductors

The mechanism of current conduction is relatively easy to visualize in the case of a metal; the metal atoms are imbedded in a “sea” of relatively free electrons, and these electrons can move as a group under the influence of an electric field. This free electron view is oversimplified, but many important conduction properties of metals can be derived from just such a model. However, we cannot account for all of the electrical properties of semiconductors in this way. Since the semiconductor has a filled valence band and an empty conduction band at 0 K, we must consider the increase in conduction band electrons by thermal excitations across the band gap as the temperature is raised. In addition, after electrons ...