5 research outputs found
Tunnel field-effect transistors for sensitive terahertz detection
The rectification of electromagnetic waves to direct currents is a crucial
process for energy harvesting, beyond-5G wireless communications, ultra-fast
science, and observational astronomy. As the radiation frequency is raised to
the sub-terahertz (THz) domain, ac-to-dc conversion by conventional electronics
becomes challenging and requires alternative rectification protocols. Here we
address this challenge by tunnel field-effect transistors made of bilayer
graphene (BLG). Taking advantage of BLG's electrically tunable band structure,
we create a lateral tunnel junction and couple it to an antenna exposed to THz
radiation. The incoming radiation is then down-converted by the tunnel junction
nonlinearity, resulting in high-responsivity (> 4 kV/W) and low-noise (0.2
pW/}) detection. We demonstrate how switching from
intraband Ohmic to interband tunneling regime can raise detectors' responsivity
by few orders of magnitude, in agreement with the developed theory. Our work
demonstrates a potential application of tunnel transistors for THz detection
and reveals BLG as a promising platform therefor
Helicity-Sensitive Plasmonic Terahertz Interferometer
Plasmonic interferometry is a rapidly growing area of research with a huge potential for applications in the terahertz frequency range. In this Letter, we explore a plasmonic interferometer based on graphene field effect transistor connected to specially designed antennas. As a key result, we observe helicity- and phase-sensitive conversion of circularly polarized radiation into dc photovoltage caused by the plasmon-interference mechanism: two plasma waves, excited at the source and drain part of the transistor, interfere inside the channel. The helicity-sensitive phase shift between these waves is achieved by using an asymmetric antenna configuration. The dc signal changes sign with inversion of the helicity. A suggested plasmonic interferometer is capable of measuring the phase difference between two arbitrary phase-shifted optical signals. The observed effect opens a wide avenue for phase-sensitive probing of plasma wave excitations in two-dimensional materials