Majority Carrier Diodes (Tunnel Diode, Backward Diode, Schottky Barrier Diode, Ohmic Contacts, and Heterojunctions)

In the recent past, the development of microwave devices having low noise, high frequency, greater bandwidth, lesser switching time etc. has yielded devices with improved performance. These devices have been used in drying machines for textile, food and papers industries etc., for biomedical applications, for electronic warfare etc. In this regard, several microwave devices have been developed. Therefore in this chapter, the majority carrier diodes for use at microwave frequencies are included. Tunnel diode: its response under zero-bias, reverse-bias, forward-bias and increased forward-bias conditions, its response beyond negative resistance region and characteristics are presented. Transitive devices, transit time effects, and requirements of a good transit time device are discussed. The backward diode, its characteristics and applications are given. Metal-semiconductor junctions, Schottky diodes: its operating mechanism, characteristics, limitations and applications are explained. Ohmic contacts, heterojunctions: their unique behaviour, band discontinuities and band bending, and potential well in it are described. Minute insight into the various topics are given through solved numerical and theoretical examples. Review questions, numerical problems and objective type questions are also given with their answers.