Diodes are used for a number of different applications, the most frequently being signal rectification, voltage clamping, reference-voltage circuits, light emitters, photodetectors, and solar cells. Usually, the diodes are based on the P-N junction. Therefore, the integrated-circuit structure of the P-N junction capacitor, shown in Fig. 2.3, represents at the same time the integrated-circuit structure of the P-N junction diode, as illustrated in Fig. 3.1. The variety of applications mentioned above can be achieved by specifically designed P-N junction diodes. The rectifying and reference P-N junction diodes are described in the first three sections of this chapter. Simultaneously, the fundamental diode-related phenomena (including breakdown) are introduced. The light emitters, photodetectors, and solar cells are introduced in Chapter 8, simultaneously with a detailed description of recombination-generation processes. The last section of this chapter is devoted to another type of diode, which is based on metal-semiconductor contact. This type of diode sometimes provides more appropriate characteristics for some applications, and also is an integral part of metal-semiconductor field-effect transistors (MESFETs).

Figure 3.1: Structure of a P-N junction diode in integrated circuits.