S. Nadar

Current driven resonant plasma wave detection of terahertz radiation: Toward the Dyakonov-Shur instability

The experiments on the dc current influence on resonant terahertz plasma wave detection in InGaAs∕InAlAs multichannel high electron mobility transistors are reported. We observed the line width shrinking when a dc current is applied. We show that this line width decrease is due to the current induced reduction of plasma wave damping and takes place because the current drives the system toward the Dyakonov-Shur plasma wave instability.

Oblique modes effect on terahertz plasma wave resonant detection in InGaAs/InAlAs multichannel transistors

We report on the demonstration of narrow terahertz plasma wave resonant detection at low temperature in 200nm gate length InGaAs∕InAlAs multichannel high electron mobility transistors. We observe that the resonant detection linewidth is smaller than in full channel high electron mobility transistors. We interpret this shrinking by the effect of multichannel geometry that does not allow oblique plasma mode propagation along the channel.

Room temperature detection of sub-terahertz radiation in double-grating-gate transistors

Room temperature photovoltaic non-resonant detection by large area double-grating-gate InGaP/InGaAs/GaAs heterostructures was investigated in sub-THz range (0.24 THz). Semi-quantitative estimation of the characteristic detection length combined with self-consistent calculations of the electric fields excited in the structure by incoming terahertz radiation allowed us to interpret quantitatively the results and conclude that this detection takes place mainly in the regions of strong oscillating electric field excited in depleted portions of the channel.

Field effect transistors for terahertz detection - silicon versus III–V material issue

Resonant frequencies of the two-dimensional plasma in FETs reach the THz range for nanometer transistor channels. Non-linear properties of the electron plasma are responsible for detection of THz radiation with FETs. Resonant excitation of plasma waves with sub-THz and THz radiation was demonstrated for short gate transistors at cryogenic temperatures. At room temperature, plasma oscillations are usually over-damped, but the FETs can still operate as efficient broadband THz detectors. The paper presents the main theoretical and experimental results on detection with FETs stressing their possible THz imaging applications. We discuss advantages and disadvantages of application of III–V GaAs and GaN HEMTs and silicon MOSFETs.

Terahertz detection in a double-grating-gate heterotransistor

We observed a photovoltaic non-resonant terahertz photoresponse in a InGaAs/GaAs heterostructure with a large area double-grating-gate at room temperature. Semi-quantitative estimation of the characteristic detection length combined with self-consistent calculations of the electric fields exited in the structure by incoming terahertz radiation allowed us to interpret this detection as coming from the depleted regions of the channel.

Sub-terahertz imaging with AlGaN/GaN MISFETs

We evaluate the optical performance of AlGaN/GaN MISFETs as a non-resonant sub-terahertz, room temperature detector. The single-pixel responsivity and the noise equivalent power are determined. The efficiency of the detection is demonstrated by the room temperature imaging of different solutions of acetone in cyclohexane.

Terahertz detection by InGaAs HEMTs in quantizing magnetic fields: Relation between magnetoresistance and photovoltaic response

THz detection by plasma wave mechanism in InGaAs HEMTs is studied in high/quantizing magnetic fields regime. The correlation between the photovoltaic response and magnetoresistance is revealed. It allows to explain the nature of strong oscillations observed in the transistor Terahertz photoresponse.