Superlattice and Other Negative-Differential-Resistance Devices: Current Status

The paper discusses and compares the concepts, performance potential, and most recent experimental results of both classical and novel active two-terminal devices for low-noise RF power generation at submillimeter- wave frequencies up to 1 THz. These devices use transit-time, transferred-electron, and quantum-mechanical effects (or a combination of them) to create a negative differential resistance at the frequency of interest. Examples of state-of-the-art results are output power levels of more than 70 mW at 62 GHz and more than 10 mW at 132 GHz from GaAs/AlGaAs superlattice electronic devices; more than 9 mW at 280 GHz, 3.7 mW at 300 GHz, 1.6 mW at 329 GHz, and more than 40 μW at 422 GHz from InP Gunn devices; and more than 140 μW at 355 GHz from a GaAs tunnel-injection transit-time diode.