Semiconductors

Abstract

In the previous chapter we saw how band theory permits the classification of solids into metals, insulators, and semiconductors. The practical use of the first two is as old as civilization. The widespread application of semiconductors, on the other hand, goes back only to the 1950s. The consequence has been a revolution in electronic technology that in turn has had large socioeconomic repercussions. It is interesting to note that the fact which triggered this revolution was not a better understanding of the physics of semiconductors. The general model of a semiconductor was developed principally by A. H. Wilson and dates back to the 1930s. The reason for the technical revolution was the advent of refining techniques that have permitted the preparation of samples of Si and Ge with impurity concentrations of 1 part in 10¹⁰. Impurity concentrations as low as a few parts per million in most other solids are difficult to obtain.