EU Fosters Terahertz Applications (TeraApps)

Werner Prost

In Europe a team of 15 young researchers will collaborate towards their PhD on the development of semiconductor based Terahertz technologies - two of them at the University Duisburg-Essen.


EU, Marie Sklodowska-Curie Innovative Training Networks: TeraApps
period 2018-2020


Research into terahertz (THz) radiation, with frequencies between 0.3 THz and 3 THz, has burgeoned in the last decade. The THz waves offer wider bandwidths, i.e. higher data rates, and improved spatial resolution compared with radio frequency electronics. Moreover, THz waves can penetrate materials such as plastics, paper and many organic compounds, including human tissue, without the hazards or potential dangers associated with ionising radiation such as X-rays. The Marie Sklodowska-Curie Innovative Training Network TeraApps coordinated by Dr. Edward Wasige, University of Glasgow shall explore the THz frequencies for applications in imaging, radar and communication.

Compact and energy-efficient, circuit components are requested for mobile THz applications. Fundamental mode oscillators hold the promise to provide the most compact and energy efficient chip-size sources up to THz frequencies. The TeraApps approach is based on resonant tunnelling diodes (RTD) on InP substrate. These diodes offer in an ultra-wide frequency range a huge negative-differential resistance that is ideally suited to de-attenuate resonators for THz emission at sufficient power up to the mW range.

A recent and very promising development is the extension of the classical two-barrier RTD design to triple barriers (TB-RTD). If the second well is different in depth and/or thickness (cf. inset Fig. 1b) a strong non-linearity in the I-V-characteristic is obtained at zero bias. For positive biasing of the device the behaviour is identical to the typical RTD behaviour exhibiting negative differential resistance. At zero bias, the non-linearity is ideally suited for RF detection. By integrating triple barriers RTD into on-chip antenna structure a combined oscillator and signal detector may be formed (Fig. 1b). Applying positive bias results in oscillator and zero bias in detector operation. RF-measurements of the fabricated devices were successfully performed with an on-wafer probe and a horn antenna positioned above the device under test. Circuit simulation based on experimental device model from our group show that powerful signal detection will be possible even at THz frequencies.

Fig. 1a Triple Barrier RTD/antenna oscillator/receiver: SEM micrograph of realized microwave detector and oscillator circuit with on-chip antenna
Fig. 1b zero bias detected microwave radiation.