Ultrahigh sensitive sub-terahertz detection by InP-based asymmetric dual-grating-gate high-electron-mobility transistors and their broadband characteristics Helicity sensitive terahertz radiation detection by field effect transistors We report on the observation of a radiation helicity sensitive photocurrent excited by terahertz (THz) radiation in dual-grating-gate (DGG) InAlAs/InGaAs/InAlAs/InP high electron mobility transistors (HEMT). For a circular polarization, the current measured between source and drain contacts changes its sign with the inversion of the radiation helicity. For elliptically polarized radiation, the total current is described by superposition of the Stokes parameters with different weights. Moreover, by variation of gate voltages applied to individual gratings, the photocurrent can be defined either by the Stokes parameter defining the radiation helicity or those for linear polarization. We show that artificial non-centrosymmetric microperiodic structures with a two-dimensional electron system excited by THz radiation exhibit a dc photocurrent caused by the combined action of a spatially periodic in-plane potential and spatially modulated light. The results provide a proof of principle for the application of DGG HEMT for all-electric detection of the radiation's polarization state. V C 2015 AIP Publishing LLC. [http://dx.

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This paper reviews recent advances in our original 2D-plasmon-resonant terahertz emitters. The structure is based on a high-electron-mobility transistor and featured with doubly interdigitated grating gates. The dual grating gates can alternately modulate the 2D electron densities to periodically distribute the plasmonic cavities along the channel, acting as an antenna. The device can emit broadband terahertz radiation even at room temperature from self-oscillating 2D plasmons under the DC-biased conditions. When the device is subjected to laser illumination, photo-generated carriers stimulate the plasma oscillation, resulting in enhancement of the emission. The first sample was fabricated with standard GaAs-based heterostructure material systems, achieving room temperature terahertz emission. The second sample was fabricated in a double-decked HEMT structure in which the grating gate metal layer was replaced with the semiconducting upper-deck 2D electron layer, resulting in enhancement of emission by one order of magnitude.

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Microscopic electroluminescence (EL) and photoluminescence (PL) measurements of high-biased AlGaN/GaN high-electron-mobility transistors are reported. We observed that the EL intensity reveals peaks around the edge of the channel and the electron temperature there is higher than the electron temperature at the center of the channel. These EL features were found to be consistent with the change in the junction temperature, which we locally estimated by comparing the PL data with measurements in raised ambient temperatures.

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Spectral analysis of the electroluminesence (EL) of AlGaN/GaN high-electron-mobility transistors is reported. The shape of the EL spectra is completely different from the shape of the photoluminescence spectrum. The wavelength for the peak of the EL spectrum gets shorter when the gate–bias voltage is decreased. Its intensity shows a bell shape when the gate-bias voltage is swept. These features suggest that the EL signal is due to the intraband transition of the channel electrons in the high-field region at the drain edge.

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