The terahertz frequency range is located between the microwave and mid-infrared regions of the electromagnetic spectrum. It has long resisted full commercial exploitation owing to difficulties in fabricating convenient sources and detectors; terahertz radiation is too high in frequency to be generated easily by the electronic techniques used in mobile telephones, but too low in frequency to be produced by the optical techniques exploited in, for example, lasers for CD players.
However, the last twenty years have witnessed a remarkable growth in the field owing to the development of innovative sources, detectors, and imaging systems. One of the innovative sources uses a semiconductor superlattice to produce a negative differential resistance at the frequencies of interest. Such a negative differential resistance undampens a resonant LC circuit and thus yields THz oscillations. State-of-the-art results were recently achieved with these superlattice electronic devices in resonant waveguide circuits.
Full integration of resonant circuits with these superlattice electronic devices greatly facilitates portable commercial applications such as medical diagnostics and ultra-wideband wireless communications far beyond current 5G technology.
The PhD project will develop and study these integrated structures and hence greatly enhance the performance boundaries of superlattice electronic devices from the current state-of-the-art results. It will include device fabrication, simulation and precision measurement.