Terahertz Electronic Devices

The frequency band of the electromagnetic spectrum between microwaves and infrared is nowadays defined as the Terahertz band (1 THz corresponds to 1012 Hz). The development of specific applications for this area requires the use of devices able to operate (for instance, as emitters, detectors, amplifiers, etc.) in this domain of extremely high frequencies. For this purpose, it is necessary to cleverly combine favourable materials and charge transport properties with specific physical mechanisms and appropriate device topologies in order to reach electrical operation in conditions that, with respect to standard electronics, can be considered as extreme. Alternative strategies (not treated in this chapter) involve either the use of optical devices or a combination of electrical and optical systems. Here, we present an overview of the main electronic devices used for applications in the Terahertz frequency domain subdivided into two-terminal devices (such as Gunn, Schottky and resonant-tunnelling diodes) and three-terminal devices (such as field-effect, heterojunction bipolar and complementary metal oxide semiconductor transistors). A section devoted to non-conventional devices exploiting ballistic transport concludes the survey.