Two-terminal millimeter-wave sources

Basic principles of operation, fundamental power-generation capabilities, and fabrication technologies are reviewed for three groups of two-terminal devices, i.e., resonant-tunneling diodes (RTDs), transferred-electron devices (TEDs), and transit-time diodes. The paper focuses on devices for frequencies above 30 GHz, and an overview of recent research in this area and of various state-of-the-art laboratory results is given. As an outlook, the potential of some new material systems for high-power devices is discussed.