Space-Charge Layers

Abstract

Space-charge layers can arise in many different kinds of physical systems. In this chapter, we shall limit the consideration to a very simple category of space-charge layers, namely those that arise in semiconductors in thermodynamic equilibrium or quasi-equilibrium. This category includes systems of considerable interest in research and technology, including semiconductor-insulator systems, p-n junctions, and Schottky barriers. In some cases, the most interesting aspect of the problem is not the space-charge layer as such but the nature of the physical mechanisms that lead to its formation. While a discussion of such mechanisms in detail is outside the scope of this chapter, we shall refer at least briefly to work bearing on such problems. Space charge layers can be detected experimentally in many different ways: by capacitance, conductance, and optical measurements, for example. The experimental methods will be described briefly in relation to particular systems.