Frequency Limitations of Resonant-Tunnelling Diodes in Sub-THz and THz Oscillators and Detectors

The review outlines the basic principles of operation of resonant-tunnelling diodes (RTDs) and RTD oscillators followed by an overview of their development in the last decades. Further, we discuss different types of RTDs and RTD oscillators, the limitations of RTDs due to parasitics, inherent limitations of RTDs and operation of RTDs as detectors. We also give an overview of the present status of sub-THz and THz RTD oscillators and give several examples of their applications.