Operation of GaN Planar Nanodiodes as THz Detectors and Mixers (original) (raw)
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GaN nanodiode arrays with improved design for zero-bias sub-THz detection
GaN based self-switching diodes (SSDs) have been fabricated for the first time on SiC substrate. They have been characterized as RF power detectors in a wide frequency range up to 220 GHz, showing a cutoff frequency of about 200 GHz. At low frequency, RF measurements exhibit a square law detection with a responsivity that well agrees with the calculations performed by means of a quasi-static model based on the shape of the I-V curve. Exploiting such a model, a simple DC characterization allows defining design rules for optimizing the practical operation of the diode arrays as RF power detectors. As strategy to improve the performance of SSDs operating as zero-bias detectors at room temperature, in terms of responsivity and noise equivalent power, we suggest: (i) the reduction of the channel width and (ii) the increase of the number of diodes in parallel in order to reduce the total device impedance to a value that coincides with 3 times that of the transmission line (or antenna) to which they are connected.
An experimental demonstration of GaN-based asymmetric nanodiodes as direct and heterodyne detectors up to 0.69 THz has been performed at room temperature. Responsivities of 2 and 0.3 V/W in a free-space configuration were obtained at 0.30 and 0.69 THz, respectively. An intermediate frequency (IF) signal has been measured up to 40 and 13 GHz in the same frequency ranges. The characterization of the nanodiodes as mixers did not show any deviation from linearity between the RF input power and the IF output. Monte Carlo simulations, used to estimate nanodevice intrinsic conversion losses of 27 dB at 0.69 THz, have confirmed these results.
0.69 THz room temperature heterodyne detection using GaN nanodiodes
GaN-based asymmetric nanodiodes have been used as heterodyne detectors up to 0.69 THz in free-space configuration where Intermediate Frequency bandwidth has been measured up 13 GHz. Monte Carlo simulations, used to estimate nano-device intrinsic conversion losses of 27 dB have confirmed these results.
GaN Heterodimensional Schottky Diode for THz Detection
2006
The performance of conventional Schottky diodes used for detecting THz radiation is limited by the RC product. Heterodimensional diodes have a smaller capacitance and series resistance. In this paper, we present the first experimental demonstration of THz detection by AlGaN/GaN heterodimensional Schottky diodes (HDSD) that exhibited reasonable performance up to at least 2.24 THz.
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.
Monte Carlo study of the operation of GaN planar nanodiodes as sub-THz emitters in resonant circuits
Semiconductor Science and Technology, 2014
A study of the high-frequency performance of GaN-based asymmetric Self-Switching Diodes (SSDs) designed for room-temperature sub-THz Gunn emission, and connected to a resonant RLC parallel circuit, is reported. With the aim of facilitating the achievement and control of Gunn oscillations, which can potentially allow the emission of THz radiation by GaN SSDs, a time-domain Monte Carlo (MC) theoretical study is provided. The simulator has been validated by the comparison with the I-V curves of similar fabricated structures, including the possibility of heating effects. V-shaped SSD has been found to be more efficient, in terms of the DC to AC conversion efficiency , than the square one. Indeed, according to our MC results, a value of of at least 0.35% @270 GHz can be achieved for the V-shaped SSD at room temperature by using an adequate resonant circuit. This value can be increased up to 0.80%, even when considering the heating effects, with appropriate RLC elements. Furthermore, simulations show that when several diodes are fabricated in parallel in order to enhance the emitted power, there is not a synchronization between the oscillations of all the SSDs; however, the phase-shift effects can be solved using a synchronized current injection by the attachment of a resonant circuit.
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.
Modelling of GaN HEMTs as Terahertz Detectors Based on Self-Mixing
Procedia Engineering, 2016
During recent years, Terahertz (THz) electronics has attracted much attention in the applications of medical, biological and industrial imaging, broadband communication etc. A GaN high-electron-mobility transistor (HEMT) is promising to work as a THz detector due to its high breakdown field, high carrier density and high temperature operation ability etc. Here we report a quasistatic self-mixing model to describe the main features of the THz response in a GaN HEMT. The model can explain not only the magnitude, but also the polarity of the photocurrent. Based on this model, we improve the gate design in GaN HEMTs from traditional symmetric pads to novel asymmetric pads. This novel gate design has been proved to be able to improve the THz detection responsivity by one order of magnitude.