Yudai Tanimoto

InP- and GaAs-Based Plasmonic High-Electron-Mobility Transistors for Room-Temperature Ultrahigh-Sensitive Terahertz Sensing and Imaging

This paper reviews recent advances in the design and performance of our original InP- and GaAs-based plasmonic high-electron-mobility transistors (HEMTs) for ultrahighly-sensitive terahertz (THz) sensing and imaging. First, the fundamental theory of plasmonic THz detection is briefly described. Second, single-gate HEMTs with parasitic antennae are introduced as a basic core device structure, and their detection characteristics and sub-THz imaging potentialities are investigated. Third, dual-grating-gate (DGG)-HEMT structures are investigated for broadband highly sensitive detection of THz radiations, and the record sensitivity and the highly-sensitive THz imaging are demonstrated using the InP-based asymmetric DGG-HEMTs. Finally, the obtained results are summarized and future trends are addressed.

Ultrahigh sensitive plasmonic terahertz detectors based on an asymmetric dual-grating gate HEMT structure

We report on ultrahigh sensitive, broadband terahertz (THz) detectors based on asymmetric double-grating-gate (A-DGG) high electron mobility transistors, demonstrating a record responsivity of 2.2 kV/W at 1 THz with a superior low noise equivalent power of 15 pW/√Hz using InGaAs/InAlAs/InP material systems. When THz radiation is absorbed strong THz photocurrent is first generated by the nonlinearity of the plasmon modes resonantly excited in undepleted portions of the 2D electron channel under the high-biased sub-grating of the A-DGG, then the THz photovoltaic response is read out at high-impedance parts of 2D channel under the other sub-grating biased at the level close to the threshold. Extraordinary enhancement by more than two orders of magnitude of the responsivity is verified with respect to that for a symmetric DGG structure.

Terahertz imaging with InP high-electron-mobility transistors

In this work, the performance of InP-based HEMTs as a THz detector was experimentally studied. The nature of the THz rectification by the two-dimensional plasmons in which the DC drain current variation ΔId becomes maximal around the threshold voltage was observed. Based on the imaging measurement, it was confirmed that our HEMTs device can work for sensitive THz imaging at 0.3 THz. The directivity of the detector was characterized with the maximum responsivity of 26.1 V/W at θ = 160 degrees.

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.