ABSTRACT
This chapter discusses the electron band structure of semiconductors and shows how the occupancy of the electron energy levels in these materials is fundamentally different from metals. The reason for this is that in semiconductors and insulators in their lowest-energy state, the electron bands are either filled or empty. This means that it is very difficult for the electrons to move under the action of an electric field because it would result in an increase in energy, and such energy states are not immediately available. Hence the conductivity is low. A vast range of semiconductor devices based on the properties of semiconductor junctions exist. These include devices which are designed for particular current-voltage characteristics, such as diodes and transistors, and optoelectronic devices such as photodetectors and photoemitters. The principles of their operation remain broadly the same. We will touch on the main concepts required for understanding them in this chapter. We will look at some of these semiconductor devices in more detail when we deal with specific applications in Chapters 11–15.
