Modelling of GaN HEMTs as Terahertz Detectors Based on Self-Mixing (original) (raw)
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2010
We report our work on development of microwave and terahertz detectors using AlN/GaN high electron mobility transistors. Microwave measurements (f = 10-40 GHz) using AlN/GaN HEMTs as detectors have been performed and the results have shown that the device work in non-resonant mode at room temperature with a responsivity roughly proportional to f 2 at low frequencies. Measured responsivity as a function of gate bias also shows reasonable agreement with theory and published results. Initial calculation results show that an AlN/GaN HEMT with 0.15 um gate length works in the resonant mode when it is cooled down to 77K. The fundamental resonant frequency increases from 200 GHz to 3.2 THz with gate-to-source voltage swing of 0.01 V to 2.0 V. The drain-to-source voltage response also increases with increasing of the gate-to-source voltage swing. We plan to integrate the AlN/GaN HEMT devices broadband lens-coupled antennas and low-pass filters for tunable plasma wave THz detectors.
Review of GaN-based devices for terahertz operation
Optical Engineering, 2017
GaN provides the highest electron saturation velocity, breakdown voltage, operation temperature, and thus the highest combined frequency-power performance among commonly used semiconductors. The industrial need for compact, economical, high-resolution, and high-power terahertz (THz) imaging and spectroscopy systems are promoting the utilization of GaN for implementing the next generation of THz systems. As it is reviewed, the mentioned characteristics of GaN together with its capabilities of providing high two-dimensional election densities and large longitudinal optical phonon of ∼90 meV make it one of the most promising semiconductor materials for the future of the THz emitters, detectors, mixers, and frequency multiplicators. GaNbased devices have shown capabilities of operation in the upper THz frequency band of 5 to 12 THz with relatively high photon densities in room temperature. As a result, THz imaging and spectroscopy systems with high resolution and deep depth of penetration can be realized through utilizing GaN-based devices. A comprehensive review of the history and the state of the art of GaN-based electronic devices, including plasma heterostructure field-effect transistors, negative differential resistances, hetero-dimensional Schottky diodes, impact avalanche transit times, quantum-cascade lasers, high electron mobility transistors, Gunn diodes, and tera field-effect transistors together with their impact on the future of THz imaging and spectroscopy systems is provided.
AlGaN/GaN HEMT’s photoresponse to high intensity THz radiation
Opto-Electronics Review, 2015
We report on the photoresponse dependence on the terahertz radiation intensity in ALGaN/GaN HEMTs. We show that the ALGaN/GaN HEMT can be used as a THz detector in CW and in pulsed regime up to radiation intensity of several kW/cm
GaN provides the highest electron saturation velocity, breakdown voltage, operation temperature, and thus the highest combined frequency-power performance among commonly used semiconductors. The industrial need for compact, economical, high-resolution, and high-power terahertz (THz) imaging and spectroscopy systems are promoting the utilization of GaN for implementing the next generation of THz systems. As it is reviewed, the mentioned characteristics of GaN together with its capabilities of providing high two-dimensional election densities and large longitudinal optical phonon of ∼90 meV make it one of the most promising semiconductor materials for the future of the THz emitters, detectors, mixers, and frequency multiplicators. GaN-based devices have shown capabilities of operation in the upper THz frequency band of 5 to 12 THz with relatively high photon densities in room temperature. As a result, THz imaging and spectroscopy systems with high resolution and deep depth of penetration can be realized through utilizing GaN-based devices. A comprehensive review of the history and the state of the art of GaN-based electronic devices, including plasma heterostructure field-effect transistors, negative differential resistances, hetero-dimensional Schottky diodes, impact avalanche transit times, quantum-cascade lasers, high electron mobility transistors, Gunn diodes, and tera field-effect transistors together with their impact on the future of THz imaging and spectroscopy systems is provided.
Operation of GaN Planar Nanodiodes as THz Detectors and Mixers
In this paper, we perform, by means of Monte Carlo simulations and experimental measurements, a geometry optimization of GaN-based nano-diodes for broadband Terahertz direct detection (in terms of responsivity) and mixing (in terms of output power). The capabilities of the so-called self-switching diode (SSD) are analyzed for different dimensions of the channel at room temperature. Signal detection up to the 690 GHz limit of the experimental set-up has been achieved at zero bias. The reduction of the channel width increases the detection responsivity, while the reduction in length reduces the responsivity but increases the cut-off frequency. In the case of heterodyne detection an intrinsic bandwidth of at least 100 GHz has been found. The intermediate frequency (IF) power increases for short SSDs, while the optimization in terms of the channel width is a trade-off between a higher non-linearity (obtained for narrow SSDs) and a large current level (obtained for wide SSDs). Moreover, the RF performance can be improved by biasing, with optimum performances reached, as expected, when the DC non-linearity is maximum.
Saturation of photoresponse to intense THz radiation in AlGaN/GaN HEMT detector
Journal of Applied Physics, 2016
We report on the photoresponse of AlGaN/GaN high electron mobility transistors to the THz radiation of low (15 mW/cm 2) and high (up to 40 kW/cm 2) intensities. We show that the response can be described by the Dyakonov-Shur theory in the whole range of radiation intensity. At low intensities, the photoresponse is linear in radiation intensity. Under intense laser radiation, we observe a saturation at intensities >20 kW/cm 2. We explain our results by the change of the channel conductivity under the influence of strong THz field. This mechanism of photoresponse saturation, which is due to the mobility decrease in high ac electric field, should exist for any type of field effect transistor detectors. Published by AIP Publishing.
Full-Wave Modeling of THz RTD-Gated GaN HEMTs
Infrared Physics & Technology, 2015
Modeling transistors at terahertz frequencies is challenging, because electromagnetic and quantum effects that are negligible in lower frequencies become limiting factors in device performance. Though previous work has focused on modeling the channel of a high-electron mobility transistor (HEMT) using hydrodynamic equations, a more complete toolset is needed to describe submillimeter-wave device gain performance. This paper introduces a simulator that couples fullwave Maxwell's equations with Schrodinger-based charge transport equations, and is used to evaluate the gain performance of a GaN HEMT at THz. This novel simulator is also used to evaluate the effect on gain when a resonant tunneling diode (RTD) is integrated with a HEMT. Upon validation with published work, we state the feasibility of RTD-gated GaN HEMT structures that have resonances up to 2.3 THz and gain up to 6 dB.
Waveguide-coupled heterodyne terahertz detector based on AlGaN/GaN high-electron-mobility transistor
Applied Physics Letters
We report a room-temperature, low output impedance, broad intermediate-frequency (IF) bandwidth field-effect terahertz detector based on an AlGaN/GaN high-electron-mobility transistor (HEMT) integrated in a metal waveguide. The waveguide detector equips a pair of quasi-Yagi antenna probes that are used to couple the terahertz energy to the HEMT channel. The gate is configured as an asymmetric edge-coupled coplanar waveguide transmission line. This terahertz electric field is asymmetrically distributed in the channel along the edges of the transmission lines. The responsivity and noise for direct and heterodyne detections are characterized and analyzed at different local oscillator (LO) powers. The noise-equivalent power in direct detection is below 189 pW/[Formula: see text]. Operated in a heterodyne mode with a LO power of −3 dBm, the detector offers a conversion loss less than 55 dB in a frequency band of 320–340 GHz. The channel in a form of transmission line performs the broad I...
Applied Physics Express, 2016
We report a sub-terahertz (THz) detector based on a 0.25-µm-gate-length AlGaN/GaN high-electron-mobility transistor (HEMT) on a Si substrate with nanoantennas. The fabricated device shows excellent performance with a maximum responsivity (R v) of 15 kV/W and a minimal noise equivalent power (NEP) of 0.58 pW/Hz 0.5 for 0.14 THz radiation at room temperature. We consider these excellent results as due to the design of asymmetric nanoantennas. From simulation, we show that indeed such nanoantennas can effectively enhance the local electric field induced by sub-THz radiation and thereby improve the detection response. The excellent results indicate that GaN HEMTs with nanoantennas are future competitive detectors for sub-THz and THz imaging applications.
Journal of Nano-and electronic Physics, 2021
Utility of the reverse double-drift region (DDR) structure has been studied for fabricating the gallium nitride impact avalanche transit time (IMPATT) diode operating at 1.0 terahertz (THz). Static and largesignal simulations have been carried out in order to verify the THz capabilities of conventional (normal) and reverse DDR structures. It is revealed that IMPATT operation is only possible in a reverse GaN DDR structure due to the lower value of series resistance of it as compared to the normal GaN DDR structure. Normal DDR GaN IMPATT cannot be operational at THz regime. Earlier, the authors had calculated the series resistance of conventional GaN DDR IMPATT diode designed to operate at 1.0 THz, however. They did not take into account the current crowing and spreading resistance at the ohmic metal contacts. That is why, the results were misleading. Those results lead to the conclusion that conventional THz GaN DDR IMPATT may produce sufficient effective negative resistance since the series resistance of it remains within the range of 1.5-2.0 Ω. In this paper, authors have proposed a reverse DDR IMPATT structure exclusively for GaN material and THz frequency bands. By using this reverse DDR structure, p +-GaN ~ Ni/Au contact can obtain a sufficient contact area, so that the anode-contact resistance can be minimized. A nonsinusoidal voltage-excited large-signal model developed by the authors has been used to study the static (DC) and large-signal properties of conventional and reverse DDR structures at 1.0 THz. The present study on the evaluation of THz source seems to open a new horizon for THz researchers and scientists.