S. Boubanga Tombet

Emission and Detection of Terahertz Radiation Using Two-Dimensional Electrons in III–V Semiconductors and Graphene

Recent advances in emission and detection of terahertz radiation using two-dimensional (2D) electron systems in III-V semiconductors and graphene are described. First the 2D plasmon resonance is presented to demonstrate intense broadband terahertz emission and detection from InGaP/InGaAs/GaAs and InAlAs/InGaAs/InP material systems. The device structure is based on a high-electron mobility transistor and incorporates the authors original asymmetrically interdigitated dual-grating gates. Second topic focuses on graphene, a monolayer carbon-atomic honeycomb lattice crystal, exhibiting peculiar carrier transport and optical properties owing to massless and gapless energy spectrum. Theoretical and experimental studies toward the creation of graphene terahertz injection lasers are described.

Ultrahigh sensitive sub-terahertz detection by InP-based asymmetric dual-grating-gate high-electron-mobility transistors and their broadband characteristics

We report on room-temperature plasmonic detection of sub-terahertz radiation by InAlAs/InGaAs/InP high electron mobility transistors with an asymmetric dual-grating-gate structure. Maximum responsivities of 22.7 kV/W at 200 GHz and 21.5 kV/W at 292 GHz were achieved under unbiased drain-to-source condition. The minimum noise equivalent power was estimated to be 0.48 pW/Hz0.5 at 200 GHz at room temperature, which is the record-breaking value ever reported for plasmonic THz detectors. Frequency dependence of the responsivity in the frequency range of 0.2–2 THz is in good agreement with the theory.

Room-Temperature, Zero-Bias Plasmonic THz Detection by Asymmetric Dual-Grating-Gate HEMT

We study theoretically and experimentally the plasmonic THz detection by the asymmetric dual-grating-gate HEMT at room temperature without source-to-drain bias. We derive the analytical expressions of photocurrents due to the plasmonic drag and ratchet effects, and we discuss about their frequency dependences. We also compare the theory to the experimentally obtained frequency dependence. It is demonstrated that they agree qualitatively well.

Terahertz-wave generation using graphene: toward the creation of graphene injection lasers

This paper reviews recent advances in terahertz-wave generation in graphene toward the creation of new types of graphene terahertz lasers. Fundamental basis of the optoelectronic properties of graphene is first introduced. Second, nonequilibrium carrier relaxation/recombination dynamics and resultant negative terahertz conductivity in optically or electrically pumped graphene are described. Third, recent theoretical advances toward the creation of current-injection graphene terahertz lasers are described. Fourth, unique terahertz dynamics of the two-dimensional plasmons in graphene are discussed. Finally, the advantages of graphene materials and devices for terahertz-wave generation are summarized.

Terahertz light amplification of stimulated emission of radiation in optically pumped graphene

The gapless and linear energy spectra of electrons and holes in graphene lead to nontrivial features such as negative dynamic conductivity in the terahertz spectral range. This paper reviews recent advances in theoretical and experimental study on terahertz light amplification by stimulated emission of radiation in optically pumped graphene.

New semiconductor materials and devices for terahertz imaging and sensing

Recent advances in materials and device structures for terahertz imaging and sensing technology are reviewed. The fundamental physical principle for terahertz imaging/sensing is focused on the nonlinear dynamics of plasmons in two-dimensional semiconductors including quantum wells in III–V based heterostructures as well as graphene.