Emission of Terahertz Radiation from Two-Dimensional Electron Systems in Semiconductor Nano- and Hetero-Structures

Abstract

This paper reviews recent advances in emission of terahertz radiation from two-dimensional (2D) electron systems in semiconductor nano-heterostructures. 2D plasmon resonance is first presented to demonstrate intense broadband terahertz emission from InGaP/InGaAs/GaAs and InAlAs/InGaAs/InP material systems. The device structure is based on a high-electron mobility transistor and incorporates the author's original interdigitated dual-grating gates. Second topic focuses on graphene, a monolayer carbon-atomic honeycomb lattice crystal, exhibiting unique carrier transport and optical properties owing to massless and gapless energy spectrum. Coherent stimulated terahertz emission from femtosecond infrared-laser pumped epitaxial graphene is experimentally observed, reflecting the occurrence of negative dynamic conductivity and population inversio

Emission and detection of terahertz radiation using two-dimensional plasmons in semiconductor nanoheterostructures for nondestructive evaluations

“…[32][33][34]39 The original structure is a S-DGG in which interfinger spaces are all identical. The device was fabricated using InGaP/InGaAs/GaAs and/or InAl/InGaAs/InP material systems.…”

“…The device was fabricated using InGaP/InGaAs/GaAs and/or InAl/InGaAs/InP material systems. 33,34 So far a broadband THz emission ranging from 1 to ∼6 THz with a maximum output power of ∼1 μW at 300 K has been obtained reflecting multimode of coherent/incoherent plasmons, 41 for which oblique modes, 42 gated and ungated plasmon modes, 43 hot plasmons, 41 and chirped plasmon modes 33 are the major causes. The DGG-HEMT THz emitter can work for THz spectroscopic and imaging applications as an incoherent broadband THz microchip source, demonstrating fine identification of water vapor absorptions as well as finger prints of sugar groups.…”

“…3(a)]. [32][33][34] The DGGs can alternately modulate the 2-D electron densities to periodically distribute the plasmonic cavities (∼100 nm width in microns distance) along the channel by applying a large fraction of gate biases for subgratings G1 and G2. [32][33][34] Under pertinent drain-source dc bias conditions, dc electron drift flows may promote the plasmon instability, resulting in self-oscillation with characteristic frequencies in the THz regime.…”

“…1 We have first proposed a 2-D plasmon-resonant microchip emitter featured with an interdigitated dual-grating gates (DGGs) structure. [32][33][34][35] The original structure uses symmetrical DGGs in which interfinger spaces are all identical, providing room-temperature 0.5-to 6.5-THz emission with 1-microwat-order radiation power 33,34 and rather low detection responsivity of the order of 10's V/W. 35 Recently, authors have proposed an asymmetric DGG (A-DGG) structure and demonstrated coherent monochromatic THz emission and ultrahigh-sensitive THz detection with 2.2 kV∕W at 1 THz radiation.…”

Emission and detection of terahertz radiation using two dimensional plasmons in semiconductor nano-heterostructures for nondestructive evaluations

“…We have first proposed a 2D-plasmon-resonant microchip emitter featured with an interdigitated dual-grating gates structure [32][33][34][35]. Original structure uses symmetrical DGG in which inter-finger spaces are all identical, providing *otsuji@riec.tohoku.ac.jp; phone 81 22 217 6104; fax 81 22 217 6104; www.otsuji.riec.tohoku.ac.jp room-temperature 0.5-6.5-THz emission with 1-microwat-order radiation power [33,34] and rather low detection responsivity of the order of 10s V/W [35].…”