| 1. |
- Svedin, Jan, et al.
(author)
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Development of a 210 GHz near-field measurement radar system based on an antenna-integrated MMIC receiver front-end and an ultra-compact HBV transmitter source module
- 2008
-
In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9780819473493 ; 7117, s. Art. no. 71170H-
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Conference paper (peer-reviewed)abstract
- The development of a 210 GHz radar system intended to study security applications such as personnel scanning is reported. The system is designed to operate with a transmit antenna floodlighting the target scene and a mechanically scanned antenna-integrated receiver module. For increased performance and potential future volume production the receiver front-end is based on highly integrated MMICs manufactured using the IAF 0.1 µm GaAs mHEMT process made available through a Swedish-German MoU. A single-chip MMIC solution is being developed containing feed antenna, LNA, mixer and an LO multiplier-chain. The transmitter part is based on a high-power HBV quintupler source-module.
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| 2. |
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| 3. |
- Banik, Biddut Kumar, 1978, et al.
(author)
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Development and Design of a 340 GHz Photomixer Source
- 2007
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In: 18th International Symposium on Space THz Technology – ISSTT 2007.
-
Conference paper (peer-reviewed)abstract
- We present the design of an InGaAlAs/InP uni-traveling-carrier photo-diode (UTC-PD) at mm-wave frequencies up to 340 GHz. The photo diode epitaxy is optimized using a quasi-3D software implementing the hydrodynamic semiconductor equations, for which an output power of 3 mW at 340 GHz was simulated. An equivalent circuit of the UTC-PD has been fitted to experimental S11 measurements up to 67 GHz. Finally, an optimized antenna coupled UTC-PD with choke filter has been designed. This MMIC circuit is intended for photomixing, with output power at 340 GHz.
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| 4. |
- Banik, Biddut Kumar, 1978, et al.
(author)
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High Power Photonic MW/THz Generation Using UTC-PD
- 2008
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In: GigaHertz SympoSium 2008. ; , s. 45-
-
Conference paper (peer-reviewed)abstract
- The ongoing research work concentrates on extending the previously accomplished UTC-PD fabrication and modelling techniques to 340 GHz and above. We have fabricated and characterized UTC-PDs intended for high power MW/THz generation. Several integrated antenna-detector circuits have been designed and characterised.
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| 5. |
- Banik, Biddut Kumar, 1978, et al.
(author)
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UTC-PD Integration for Submillimetre-wave Generation
- 2008
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In: 19th International Symposium on Space Terahertz Technology, ISSTT 2008; Groningen; Netherlands; 28 April 2008 through 30 April 2008. ; , s. P7-1, 135
-
Conference paper (peer-reviewed)abstract
- Because of the inherent difficulty to generate power in the frequency range 0.l-10 THz, the term 'THzgap' has been coined. Among a number of MW/THz generation techniques, the photomixer based sources hold high potential offering wide tunability and decent amounts of output power. The photomixing technique relies on the nonlinear mixing of two closely spaced laser wavelengths generating a beat oscillation at the difference frequency. In recent years, there has been an increasing interest in the Uni-Travelling-Carrier PhotoDiode (UTCPD) [1] for photomixing, photo receivers, MW/THz-wave generation, fibre-optic communication systems, and wireless communications. UTC-PDs have become very promising by demonstrating output powers of 20 mW at 100 GHz [1] and 25 μW at 0.9 THz [2].
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| 6. |
- Bryllert, Tomas, 1974, et al.
(author)
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220-GHz imaging radar with 1 Hz frame rate using an array of homodyne transceivers
- 2018
-
In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 10634
-
Conference paper (peer-reviewed)abstract
- We present a 220 GHz imaging radar prototype that has been developed in the European Defense Agency (EDA) project TIPPSI. The purpose of the development was to demonstrate short-range high-resolution 3D imaging for security applications at checkpoints, and to guide the development of stand-off real-time millimeter wave and sub-millimeter wave imaging systems for detection of larger objects at greater distances. An additional goal was to experimentally verify simulation techniques for active (sub)-mmw imaging systems, the verified simulation techniques can then be used to explore different system architectures. The 220 GHz imaging radar prototype consist of a flexible, mechanically scanned optical system that can support linear arrays of transmit/receive (TxRx) units up to 150 mm in length. The optical system is divided into two parts: A compact Dragonian system including the mechanical scanner that can be used as a stand-alone imager at reduced target distance and resolution, and a confocal system that can be added to achieve the full resolution of 1 cm x 1 cm x 1 cm at 4.5 m target distance. The field of view of the full resolution system is 70 cm x 70 cm. The front-end is currently populated by 4 TxRx units that are sparsely distributed along the 150 mm focal plane. The TxRx units operate in frequency modulated continuous wave (FMCW) mode and have a bandwidth of 24 GHz. Each TxRx unit use a single horn antenna and the transmit- and receive signals are generated and received using the same circuits which avoids the need of a duplexer. We will demonstrate high resolution 3D videos taken at 1 Hz frame rate and compare the individual images with simulations using electromagnetic simulators and character/clothes animation.
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| 7. |
- Fobelets, Kristel, et al.
(author)
-
High-frequency capacitance of bipolar resonant tunneling diodes
- 1996
-
In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 79:2, s. 905-910
-
Journal article (peer-reviewed)abstract
- The high-frequency characteristics of bipolar resonant tunneling diodes are experimentally investigated at room temperature. The electron accumulation and discharging in these resonant tunneling light-emitting diodes are studied at frequencies up to 35 GHz. The experiments show capacitance peaks due to electron charge disappearing from the quantum well. The measurements are found to be in agreement with our theoretical model for the calculation of the high-frequency characteristics of resonant tunneling devices. The high-frequency characteristics of the bipolar light-emitting resonant tunneling diode are compared to the unipolar resonant tunneling diode and the resonant interband tunneling diode. The comparison shows a similar discharging characteristic of the quantum well, but a different overall variation of the capacitance.
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| 8. |
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| 9. |
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| 10. |
- Majdi, Saman, 1977-, et al.
(author)
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Enhanced Hall mobility in graphene-on-electronic-grade diamond
- 2023
-
In: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 123:1
-
Journal article (peer-reviewed)abstract
- The outstanding electronic properties of graphene make this material a candidate for many applications, for instance, ultra-fast transistors. However, self-heating and especially the detrimental influence of available supporting substrates have impeded progress in this field. In this study, we fabricate graphene-diamond heterostructures by transferring graphene to an ultra-pure single-crystalline diamond substrate. Hall-effect measurements were conducted at 80 to 300 K on graphene Hall bars to investigate the charge transport properties in these devices. Enhanced hole mobility of 2750 cm(2) V-1 s(-1) could be observed at room-temperature when using diamond with reduced nitrogen (N-s(0)) impurity concentration. In addition, by electrostatically varying the carrier concentration, an upper limit for mobility is determined in the devices. The results are promising for enabling carbon-carbon (C-C) devices for room-temperature applications.
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| 11. |
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| 12. |
- Sobis, Peter, 1978, et al.
(author)
-
SWI 1200/600 GHz highly integrated receiver front-ends
- 2015
-
In: 36th ESA Antenna Workshop on Antennas and RF Systems for Space Science, ESA/ESTEC ,Noordwijk, The Netherlands; 6-9 Oct. 2015. ; session S3.1.2
-
Conference paper (peer-reviewed)
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| 13. |
- Sobis, Peter, 1978, et al.
(author)
-
Ultra Low Noise 600/1200 GHz and 874 GHz GaAs Schottky Receivers for SWI and ISMAR
- 2016
-
In: Twenty-seventh International Symposium on Space Terahertz Technology (ISSTT).
-
Conference paper (peer-reviewed)abstract
- Omnisys Instruments is responsible for the 600/1200 GHz broadband front-end receivers and back-end spectrometer hardware for the Submillimeter Wave Instrument (SWI) part of the Jupiter Icy moons Explorer (JUICE) mission, and for the development of the dual-polarization 874 GHz spectrometer channels for the airborne icecloud imager instrument ISMAR. We will present our development of these highly integrated heterodyne receivers which are based on membrane integrated GaAs Schottky diode mixer and multiplier circuit technology, and InP HEMT MMIC LNA technology from Chalmers University of Technology. Preliminary results at room temperature on the 1200 GHz breadboard prototypes show on a typical DSB receiver noise below 3000 K in the 1030 GHz-1220 GHz frequency range with only 1-3 mW of LO power. For the 874 GHz receiver flight modules a record low double sideband noise of 2500 K was obtained with only 2.3 mW of LO pump power. Both the 1200 GHz and 874 GHz subharmonically pumped Schottky mixer designs have been based on the broadband SWI 600 GHz channel mixer design, which had a repeatable receiver noise performance below 1200K with less than 2 mW of pump power at room temperature. All together these results are setting new standards for critical receiver hardware operating at room temperature used in instrumentation for atmospheric research and remote sensing applications.
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| 14. |
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| 15. |
- Svedin, Jan, et al.
(author)
-
An experimental 210 GHz radar system for 3D stand-off detection
- 2010
-
In: 35th International Conference on Infrared Millimeter and Terahertz Waves (IRMMW-THz), 2010. - 9781424466559
-
Conference paper (peer-reviewed)abstract
- A 210 GHz radar system for studies of personscanning at stand-off distances is presented. The radar uses amechanically scanned RX front-end based on an antennaintegratedMMIC. The TX part is based on an HBV quintupler.Image data formation is made using the FMCW and SARprinciples.
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| 16. |
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| 17. |
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| 18. |
- Tavakoli Dastjerdi, Mohammad Hadi, 1984, et al.
(author)
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InGaAs/InAlAs/AlAs Heterostructure Barrier Varactors on Silicon Substrate
- 2011
-
In: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 32:2, s. 140-142
-
Journal article (peer-reviewed)abstract
- We present the results of a study on epitaxial transferof InP-based heterostructure barrier varactor (HBV) materials onto a silicon substrate employing the low-temperature plasma activated bonding technique. The test diodes fabricated on the bonded samples exhibit symmetric electrical characteristics, over the temperature range of 25 ˚C–165 ˚C, and show no degradation compared to previously reported InP-based diodes. Moreover, the onset temperature for debonding, the effective barrier height extracted from the measured data, and the maximum voltage of the HBVs for a current density of 100 A/cm2 were extracted to be 260 ˚C, 0.56 eV, and 10.5 V, respectively.
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| 19. |
- Tavakoli Dastjerdi, Mohammad Hadi, 1984, et al.
(author)
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Transfer of InP-based HBV epitaxy onto borosilicate glass substrate by anodic bonding
- 2010
-
In: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 46:14, s. 1013-1014
-
Journal article (peer-reviewed)abstract
- We present a new fabrication process for epitaxial transfer of InP-based heterostructure barrier varactor diodes, as high frequency varactor multipliers, onto low-dielectric borosilicate glass substrate, employing anodic bonding. The fabricated diodes on the new host substrate display symmetric electrical characteristics with only minor differences compared to those of the reference devices on the original InP substrate.
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| 20. |
- Vukusic, Josip, 1972, et al.
(author)
-
Development of Uni-Travelling-Carrier Photodiodes
- 2006
-
In: 4th ESA Workshop on Millimetre Wave Technology and Applications.
-
Conference paper (peer-reviewed)abstract
- We have fabricated and characterized InGaAsP/InP uni-travelling-carrier photodiodes (UTC-PDs). An UTC-PD layer structure in the material system InGaAlAs/InP was also designed and grown with in-house molecular beam epitaxy (MBE). Using standard III-V processing involving lithography, metallization and etching, diodes of different sizes have been fabricated. Time domain and eye-diagram measurements have been performed. Limitations in the measurement system were identified and compensated for when measuring the bandwidth. The resulting bandwidth is in agreement with the area dependent RC-limitation which was estimated using quasi-DC capacitance-voltage (C-V) measurements.
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| 21. |
- Vukusic, Josip, 1972, et al.
(author)
-
Fabrication and Characterization of InGaAlAs/InP based Uni-Traveling-Carrier Photodiodes
- 2006
-
In: The Joint 31st International Conference on Infrared and Millimeter Waves and 14th International Conference on Terahertz Electronics. - 1424404002 ; , s. 138-
-
Conference paper (peer-reviewed)abstract
- We have fabricated and characterized InGaAlAs/InP uni-traveling-carrier photodiodes intended for photo-mixing and data-com applications. Bandwidths up to 60GHz were recorded with 8.5µm diameter devices for which a matched, integrated antenna-detector circuit has been designed.
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| 22. |
- Wiberg, Andreas, 1978, et al.
(author)
-
Characterization of uni-traveling carrier photodiodes for high-linearity and high-SNR applications
- 2010
-
In: Microwave and Optical Technology Letters. - : Wiley. - 1098-2760 .- 0895-2477. ; 52:6, s. 1460-1460
-
Journal article (peer-reviewed)abstract
- A typical uni-traveling carrier photodiode (UTC-PD) and a commercial PIN-PD are compared in the context of the analog performance at 10 GHz in a realistic noise environment.The behavior of the carrier-to-noise ratio (CNR), the linearity, represented by the third-order output intercept point (OIP3), and the spurious free dynamic range are studied as a function of photocurrent. We have found that the increment of the CNR is only minor because of excess noise of the amplifier, as an optical amplifier is used to reach high optical power. However, the OIP3 of the UTC-PD is substantially higher and increases with photocurrent, in contrast to the PIN-PD. Thus, even though the responsivity is lower, it is beneficial to use a UTC-PD to have superior dynamic range.
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| 23. |
-
Abstract Book of the 30th Workshop on Compound Semiconductor Devices and Integrated Circuits in Europe
- 2006
-
Editorial collection (peer-reviewed)abstract
- The organisers and hosts warmly welcome you to the 30th Workshop on Compound Semiconductor Devices and Integrated Circuits in Europe, WOCSDICE 2006, at the Gullmarsstrand Hotel & Conferences in Fiskebäckskil, Sweden, May 14-17, 2006. The symposium is organised by the Chalmers Department of Microtechnology and Nanoscience (MC2) with the aim to create a forum where researchers can discuss latest results and trends in the field of compound semiconductor technology and related science. Established in 1973, WOCSDICE has a long-standing tradition. This workshop brings together both internationally recognised researchers and promising young scientists and engineers to disseminate state-of-the-art research findings in the areas of compound semiconductor materials, associated devices and integrated circuits. This year we have 56 papers (8 invited) divided into nine sessions and more than 78 delegates from 20 countries.Fiskebäckskil is a small restful community situated by Gullmarsfjorden opposite to the village Lysekil. Gullmarsfjorden is Sweden's only true threshold fjord, 25 km deep and 1 to 3 km broad. In the 19th century the small fishing village was transformed into a shipping society. The special wood based architecture of this time is well preserved until today. During the 20th century Fiskebäckskil, surrounded by red granite and the salty sea became a prime choice for summer recreation and swimming. The conference hotel (Gullmarsstrand) building is reverentially renovated and modernised to fulfil the highest expectations for a successful workshop.The workshop is sponsored by the Swedish Research Council (VR), the IEEE Sweden Section, the Swedish Foundation for Strategic Research (SSF-HSEP), Swedish Governmental Agency for Innovation Systems (VINNOVA), OXFORD Plasma Technology and Agilent technologies. We would like to thank these organisations for their support. We would also like to thank everyone who helped to arrange WOCSDICE 2006: the international steering committee for advice; the local organising committee; Eva Hellberg and Peter Jönsson for all WEB support; Catharina Forssén, and Ingrid Collin for help with registrations and payments; the session chairs; and everyone who attends or contributes with a presentation.On behalf of the local organisation committee, we would like to welcome all of you and wish you a pleasant and fruitful stay in Fiskebäckskil.Welcome!Jan Stake and Jan GrahnWOCSDICE2006 Chairmen
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| 24. |
- Ahlberg Gagnér, Viktor, 1989, et al.
(author)
-
Clustering of atomic displacement parameters in bovine trypsin reveals a distributed lattice of atoms with shared chemical properties
- 2019
-
In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 9:1
-
Journal article (peer-reviewed)abstract
- Low-frequency vibrations are crucial for protein structure and function, but only a few experimental techniques can shine light on them. The main challenge when addressing protein dynamics in the terahertz domain is the ubiquitous water that exhibit strong absorption. In this paper, we observe the protein atoms directly using X-ray crystallography in bovine trypsin at 100 K while irradiating the crystals with 0.5 THz radiation alternating on and off states. We observed that the anisotropy of atomic displacements increased upon terahertz irradiation. Atomic displacement similarities developed between chemically related atoms and between atoms of the catalytic machinery. This pattern likely arises from delocalized polar vibrational modes rather than delocalized elastic deformations or rigid-body displacements. The displacement correlation between these atoms were detected by a hierarchical clustering method, which can assist the analysis of other ultra-high resolution crystal structures. These experimental and analytical tools provide a detailed description of protein dynamics to complement the structural information from static diffraction experiments. © 2019, The Author(s).
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| 25. |
- Alderman, Byron, et al.
(author)
-
A New Pillar Geometry for Heterostructure Barrier Varactor Diodes
- 2001
-
In: 12th International Symposium on Space Terahertz Technology. ; , s. 330-339
-
Conference paper (peer-reviewed)abstract
- We report on a novel diode geometry, with reduced thermal resistance, for Heterostructure Barrier Varactor, HBV, diodes. The pillar geometry presented here involves the complete removal of the substrate, electrical contacted is made by the forward and reverse side processing of metallic pillars. We propose that there is a limit to the maximum number of barriers that can be used to increase the power capability of a HBV. An analytical model has been developed to study these effects. In considering the case of a perfect thermal heat sink the limit is found to be fourteen, in applying this model to the new pillar structure this is reduced to six.
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| 26. |
- Amirmazlaghani, Mina, 1984, et al.
(author)
-
Graphene-Si Schottky IR Detector
- 2013
-
In: IEEE Journal of Quantum Electronics. - 0018-9197 .- 1558-1713. ; 49:7, s. 589-594
-
Journal article (peer-reviewed)abstract
- This paper reports on photodetection properties of graphene-Si schottky junction by measuring current-voltage characteristics under 1.55µm excitation laser. The measurements have been done on a junction fabricated by depositing mechanically exfoliated natural graphite on top of the pre-patterned silicon substrate. The electrical Schottky barrier height is estimated to be (0.44-0.47) eV with a minimum responsivity of 2.8mA/W corresponding to an internal quantum efficiency of 10% which is almost an order of magnitude larger than regular Schottky junctions. A possible explanation for the large quantum efficiency related to the 2-D nature of graphene is discussed. Large quantum efficiency, room temperature IR detection, ease of fabrication along with compatibility with Si devices can open a doorway for novel graphene-based photodetectors.
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| 27. |
- Anderberg, Martin, 1992, et al.
(author)
-
A 183-GHz Schottky diode receiver with 4 dB noise figure
- 2019
-
In: IEEE MTT-S International Microwave Symposium Digest. - : IEEE. - 0149-645X. ; 2019-June, s. 172-175
-
Conference paper (peer-reviewed)abstract
- Atmospheric science based on space-borne millimeter wave measurements require reliable and state-of-the art receivers. In particular, the water vapor line at 183.3 GHz motivates the development of sensitive mixers at this frequency. Traditional assembly techniques employed in the production of Schottky diode receivers involve flip-chip mounting and soldering of discrete dies, which prohibit the implementation of reliable and repeatable production processes. In this work, we present a subharmonic 183 GHz mixer implementing a repeatable assembly method using beamlead Schottky diodes. The mixer was integrated with a InP HEMT MMIC low noise intermediate frequency amplifier resulting in a record-low receiver noise temperature of 450 K at 1 mW of local oscillator power measured at room-temperature. The measured Allan time was 10 s and the third order local oscillator spurious power was less than -60 dBm. The proposed assembly method is of particular importance for space-borne missions but also applicable to a wide range of terahertz applications.
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| 28. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
-
10 dB small-signal graphene FET amplifier
- 2012
-
In: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 48:14, s. 861-863
-
Journal article (peer-reviewed)abstract
- Reported is the realisation of a graphene FET microwave amplifier operating at 1 GHz, exhibiting a small-signal power gain of 10 dB and a noise figure of 6.4 dB. The amplifier utilises a matching inductor on the gate yielding a return loss of 20 dB. The design is optimised for maximum gain and the optimum noise figure is extracted by noise modelling and predicted to be close to 1 dB for the intrinsic graphene FET at this frequency. The presented results complement existing graphene FET applications and are promising for future graphene microwave circuits.
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| 29. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
-
A 185-215-GHz Subharmonic Resistive Graphene FET Integrated Mixer on Silicon
- 2017
-
In: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 65:1, s. 165-172
-
Journal article (peer-reviewed)abstract
- A 200-GHz integrated resistive subharmonic mixer based on a single chemical vapor deposition graphene field-effect transistor (G-FET) is demonstrated experimentally. This device has a gate length of 0.5 μm and a gate width of 2x40 μm. The G-FET channel is patterned into an array of bow-tie-shaped nanoconstrictions, resulting in the device impedance levels of ~50 Ω and the ON-OFF ratios of ≥4. The integrated mixer circuit is implemented in coplanar waveguide technology and realized on a 100-μm-thick highly resistive silicon substrate. The mixer conversion loss is measured to be 29 ± 2 dB across the 185-210-GHz band with 12.5-11.5 dBm of local oscillator (LO) pump power and >15-dB LO-RF isolation. The estimated 3-dB IF bandwidth is 15 GHz.
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| 30. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
-
An Accurate Empirical Model Based on Volterra Series for FET Power Detectors
- 2016
-
In: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 64:5, s. 1431-1441
-
Journal article (peer-reviewed)abstract
- An empirical model for field-effect transistor (FET) based power detectors is presented. The electrical model constitutes a Volterra analysis based on a Taylor series expansion of the drain current together with a linear embedding small-signal circuit. It is fully extracted from S-parameters and IV curves. The final result are closed-form expressions for the frequency dependence of the noise equivalent power (NEP) in terms of the FET intrinsic capacitances and parasitic resistances. Excellent model agreement to measured NEP of coplanar access graphene FETs with varying channel dimensions up to 67 GHz is obtained. The influence of gate length on responsivity and NEP is theoretically and experimentally studied.
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| 31. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
-
Comparison of carrier scattering mechanisms in chemical vapor deposited graphene on fused silica and strontium titanite substrates
- 2014
-
In: Graphene Week 2014.
-
Conference paper (peer-reviewed)abstract
- Graphene is explored for numerous applications for both electronics and photonics. These range from high frequency and low noise field effect transistors to conductive and highly transparent LED electrodes. To exploit the full potential of graphene, the remarkable intrinsic carrier transport properties and tunable, potentially low sheet resistance must be efficiently utilized. However, graphene carrier mobility is currently strongly degraded by extrinsic factors arising mainly from the dielectric environment, i.e. substrate and gate oxide. A proposed route to enhance transport is the use of a high-κ substrate to screen charged impurities at the graphene-substrate interface. In this paper, mobility and carrier concentration in CVD grown graphene films on fused silica (FS, κ=3.9) and strontium titanite (STO, κ=300) substrates are extracted from microwave measurements and compared to Hall data. To model the mobilities scattering by charged impurities (CI), substrate polar phonons (SPP) and resonant centers (RS) are included. Resonant scatterers dominates on strontium titanite and together with charged impurities on fused silica. While resonant scatterers are likely reduced by moving from wet to dry graphene transfer methods, the nominal mobility improvement by screening of charged impurities on high- κ strontium titanite would be masked at room temperature by increased surface phonon scattering.
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| 32. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
-
Extraction of carrier transport properties in graphene from microwave measurements
- 2014
-
In: European Microwave Conference (EuMC), 2014 44th. ; , s. 359 - 362
-
Conference paper (peer-reviewed)abstract
- Carrier transport parameters of graphene grown by chemical vapor deposition (CVD) and graphene-metal contacts are extracted from microwave measurements in the frequency range 0.1–20 GHz using Corbino disks. It is shown that the charged impurities are effectively screened by the high permittivity of the SrTiO3 substrate. In the case of fused silica substrate the charged impurities are not completely screened and the mobility is limited either by the charged impurities or/and resonant scatterers depending on their relative concentration.
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| 33. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
-
Feasibility of Ambient RF Energy Harvesting for Self-Sustainable M2M Communications Using Transparent and Flexible Graphene Antennas
- 2016
-
In: IEEE Access. - 2169-3536 .- 2169-3536. ; 4, s. 5850-5857
-
Journal article (peer-reviewed)abstract
- Lifetime is a critical parameter in ubiquitous, battery-operated sensors for machine-to-machine (M2M) communication systems, an emerging part of the future Internet of Things. In this practical article, the performance of radio frequency (RF) to DC energy converters using transparent and flexible rectennas based on graphene in an ambient RF energyharvesting scenario is evaluated. Full-wave EM simulations of a dipole antenna assuming the reported state-of-the-art sheet resistance for few-layer, transparent graphene yields an estimated ohmic efficiency of 5 %. In the power budget calculation, the low efficiency of transparent graphene antennas is an issue because of the relatively low amount of available ambient RF energy in the frequency bands of interest, which together sets an upper limit on the harvested energy available for the RF-powered device. Using a commercial diode rectifier and an off-the-shelf wireless system for sensor communication, the graphene-based solution provides only a limited battery lifetime extension. However, for ultra-low-power technologies currently at the research stage, more advantageous ambient energy levels, or other use cases with infrequent data transmission, graphene-based solutions may be more feasible.
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| 34. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
-
Microwave characterization of Ti/Au-graphene contacts
- 2013
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 103:17, s. 173111-
-
Journal article (peer-reviewed)abstract
- In this paper, we report on a microwave characterization of the interface between Ti/Au contacts and chemical vapor deposition graphene using structures of Corbino geometry, with primary focus on extracting and modeling the capacitance associated with the contact region. It is found that with the current contact resistivity, ρc∼10^−6 Ωcm2, the contact capacitance, on the order Cc∼1 μF/cm2, has a negligible effect on microwave transmission through the contact below ∼100 GHz. Finally, a parallel plate capacitance model for the contact is presented.
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| 35. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
-
Noise Figure Characterization of a Subharmonic Graphene FET Mixer
- 2012
-
In: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. - 9781467310871
-
Conference paper (peer-reviewed)abstract
- We report on the first room temperature noise figure measurement of a graphene FET subharmonic resistive mixer in the interval fRF = 2-5 GHz. Due to an 8 nm thin Al2O3 gate dielectric it can operate with a conversion loss in the range 20-22 dB at only 0 dBm of local oscillator power. The measurement yields a noise figure close to the conversion loss, thus determining the noise to be thermal in origin, which is promising for cryogenic applications. The general route to lower noise figure is an improvement of the conversion loss.
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| 36. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
-
Resistive Graphene FET Subharmonic Mixers: Noise and Linearity Assessment
- 2012
-
In: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 60:12, s. 4035-4042
-
Journal article (peer-reviewed)abstract
- We report on the first complete RF characterization of graphene field-effect transistor subharmonic resistive mixers in the frequency interval 2–5 GHz. The analysis includes conversion loss (CL), noise figure (NF), and intermodulation distortion. Due to an 8-nm thin Al2O3 gate dielectric, the devices operate at only 0 dBm of local oscillator (LO) power with an optimum measured CL in the range of 20–22 dB. The NF closely mimics the CL, thus determining the noise to be essentially thermal in origin, which is promising for cryogenic applications. The highest input third-order intercept point is measured to be 4.9 dBm at an LO power of 2 dBm.
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| 37. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
-
Towards Graphene Electrodes for High Performance Acoustic Resonators
- 2013
-
In: WOCSDICE. ; , s. 99-100
-
Conference paper (peer-reviewed)abstract
- The tunable FBAR is a promising building block for versatile microwave systems. Utilizing graphene electrodes promises higher tunability and frequency. Increased parasitic resistance may hamper the Q-factor of the resonator. This paper reports the initiated study of graphene and contacts at DC and microwave frequencies for optimization of these parameters leading to graphene FBARs.
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| 38. |
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| 39. |
- Asad, Muhammad, 1986, et al.
(author)
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Correlation between material quality and high frequency performance of graphene field-effect transistors
- 2019
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Conference paper (other academic/artistic)abstract
- Correlations between material quality, equivalent circuit and high frequency parameters of the graphene field-effect transistors, such as mobility, contact resistivity, carrier velocity, drain conductivity, transit frequency and maximum frequency of oscillation, have been established via applying drain resistance, velocity and saturation velocity models. The correlations allow for understanding dominant limitations of the high frequency performance of transistors, which clarifies the ways of their further development. In particular, the relatively high drain conductivity is currently main limiting factor, which, however, can be counterbalanced by increasing the carrier velocity via operating transistors at higher fields, in the velocity saturation mode.
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| 40. |
- Asad, Muhammad, 1986, et al.
(author)
-
Enhanced high-frequency performance of top-gated graphene FETs due to substrate-induced improvements in charge carrier saturation velocity
- 2021
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In: IEEE Transactions on Electron Devices. - 1557-9646 .- 0018-9383. ; 68:2, s. 899-902
-
Journal article (peer-reviewed)abstract
- High-frequency performance of top-gated graphene field-effect transistors (GFETs) depends to a large extent on the saturation velocity of the charge car-riers, a velocity limited by inelastic scattering by surface optical phonons from the dielectrics surrounding the chan-nel. In this work, we show that by simply changing the graphene channel surrounding dielectric with a material having higher optical phonon energy, one could improve the transit frequency and maximum frequency of oscillation of GFETs. We fabricated GFETs on conventional SiO2/Si substrates by adding a thin Al2O3 interfacial buffer layer on top of SiO2/Si substrates, a material with about 30% higher optical phonon energy than that of SiO2, and compared performance with that of GFETs fabricated without adding the interfacial layer. From S-parameter measurements, a transit frequency and a maximum frequency of oscillation of 43 GHz and 46 GHz, respectively, were obtained for GFETs on Al2O3 with 0.5 µm gate length. These values are approximately 30% higher than those for state-of-the-art GFETs of the same gate length on SiO2. For relating the improvement of GFET high-frequency performance to improvements in the charge carrier saturation velocity, we used standard methods to extract the charge carrier veloc-ity from the channel transit time. A comparison between two sets of GFETs with and without the interfacial Al2O3 layer showed that the charge carrier saturation velocity had increased to 2·10^7 cm/s from 1.5·10^7 cm/s.
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| 41. |
- Asad, Muhammad, 1986, et al.
(author)
-
Graphene field-effect transistors for high frequency applications
- 2018
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In: ; November 2018
-
Conference paper (peer-reviewed)abstract
- Realization of competitive high frequency graphene field-effect transistors (GFETs) is hindered, in particular, by extrinsic scattering of charge carriers and relatively high contact resistance of the graphene-metal contacts, which are both defined by the quality of the corresponding graphene top interfaces [1]. In this work, we report on improved performance of GFETs fabricated using high quality chemical vapour deposition (CVD) graphene and modified technology steps. The modified processing flow starts with formation of the gate dielectric, which allows for preserving the high velocity of charge carriers, and, simultaneously, providing very low contact resistance. The transfer line method (TLM) analysis and fitting the GFET transfer characteristics (Fig. 1) both reveal very low specific width contact resistivity of the top contacts, down to 95 Ω⋅μm. Fitting shows also that the field-effect mobility in the GFETs can be up to 5000 cm2/(V⋅s). The measured (extrinsic) transit frequency (fT) and the maximum frequency of oscillation (fmax) are up to 35 GHz and 40 GHz, respectively, for GFETs with gate length Lg=0.5 μm (Fig. 2), which are highest among those reported so far for the GFETs with similar gate length and comparable with those of Si MOSFETs [2,3]. The dependencies of the fT and fmax on the gate length indicate that these GFETs are very promising for the scaling down and in particular for the development of power amplifiers operating in the mm-wave frequency range.
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| 42. |
- Asad, Muhammad, 1986, et al.
(author)
-
The dependence of the high-frequency performance of graphene field-effect transistors on channel transport properties
- 2020
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In: IEEE Journal of the Electron Devices Society. - 2168-6734. ; 8, s. 457-464
-
Journal article (peer-reviewed)abstract
- This paper addresses the high-frequency performance limitations of graphene field-effect transistors (GFETs) caused by material imperfections. To understand these limitations, we performed a comprehensive study of the relationship between the quality of graphene and surrounding materials and the high-frequency performance of GFETs fabricated on a silicon chip. We measured the transit frequency (fT) and the maximum frequency of oscillation (fmax) for a set of GFETs across the chip, and as a measure of the material quality, we chose low-field carrier mobility. The low-field mobility varied across the chip from 600 cm2/Vs to 2000 cm2/Vs, while the fT and fmax frequencies varied from 20 GHz to 37 GHz. The relationship between these frequencies and the low-field mobility was observed experimentally and explained using a methodology based on a small-signal equivalent circuit model with parameters extracted from the drain resistance model and the charge-carrier velocity saturation model. Sensitivity analysis clarified the effects of equivalent-circuit parameters on the fT and fmax frequencies. To improve the GFET high-frequency performance, the transconductance was the most critical parameter, which could be improved by increasing the charge-carrier saturation velocity by selecting adjacent dielectric materials with optical phonon energies higher than that of SiO2.
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| 43. |
- Auriacombe, Olivier, 1989, et al.
(author)
-
325 GHz and 650 GHz Dual-polarisation receivers Concept
- 2022
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In: 32nd International Symposium of Space Terahertz Technology, ISSTT 2022.
-
Conference paper (peer-reviewed)abstract
- The integrated dual-polarisation receivers utilize a dual probe concept, efficiently integrating the antenna and MMIC package environment which allows for polarisation discrimination without the use of bulky and lossy external orthomode transducers. This concept increases the sensitivity of the instrument and reduces its size, enabling the development of future earth observation arrays. Omnisys Instruments AB (Sweden) and Chalmers University of Technology (Sweden) are working to demonstrate state-of-the-art dual polarisation capability with two integrated receiver modules at 325 GHz and 650 GHz.
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| 44. |
- Banik, Biddut Kumar, 1978, et al.
(author)
-
A novel catadioptric dielectric lens for microwave and terahertz applications
- 2008
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In: Microwave and Optical Technology Letters. - : Wiley. - 1098-2760 .- 0895-2477. ; 50:2, s. 416-419
-
Journal article (peer-reviewed)abstract
- A novel dielectric catadioptric lens, suitable for near-field sensing and imaging, is presented. The focusing property and the far-field pattern of the lens are investigated using a 3D full-wave electromagnetic solver. Furthermore, the proposed catadioptric lens has been designed and fabricated from Delrin. Simulations and measurements of the far-field at 5 GHz and return loss versus frequency using a Bow-tie slot feeding antenna are presented.
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| 45. |
- Banik, Biddut Kumar, 1978, et al.
(author)
-
Catadioptric Dielectric Lens for Imaging Applications
- 2008
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In: Proceedings of 33rd International Conference on Infrared, Millimeter, and Terahertz Waves. - 9781424421190 ; , s. 1 - 2
-
Conference paper (peer-reviewed)abstract
- The design and characterization results of a novel catadioptric dielectric lens are presented. Although being electrically small, the lens provides a focus in the close vicinity which makes it suitable to be used in microwave and terahertz systems. Several lenses of different dielectric materials and dimensions have been fabricated. A simple backscattering measurement method has been implemented in order to determine the focusing property of the lens.
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| 46. |
- Banik, Biddut Kumar, 1978, et al.
(author)
-
Design of Antenna Integrated Photomixers and Catadioptric Lenses for Emerging THz Applications
- 2008
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In: 2008 ANSYS Regional Conference.
-
Conference paper (other academic/artistic)abstract
- We will present design and modeling of antenna integrated photomixers for terahertz generation. In addition, the design and the quasioptical integration a novel catadioptric dielectric lens, suitable for imaging applications, will be presented. Although having a tremendous potential, the terahertz (0.1 – 10 THz) regime in the frequency spectrum and its applications are hindered due to the lack of viable and high power terahertz sources. This has led to the term “terahertz gap” being coined. We aim to construct compact sources utilizing the lens-coupled antenna-integrated photomixer sources based on Uni-Travelling-Carrier Photomixers (UTC-PD). These sources are one of the key components which could significantly bridge the terahertz gap.However, optimization of the epitaxial layer structure of the UTC-PD is necessary for high-power THz generation. The epilayers of the UTC-PD is designed and optimized in TCAD. Antennas are designed using HFSS while the impedance of the antenna at a specific bandwidth from HFSS is used to optimize the UTC-PD epilayers and vice versa. Thus proper impedance match and therefore high power THz generation is possible.A novel catadioptric dielectric lens is designed and characterized using HFSS. The lens provides an alternative solution to be used as a focusing element and therefore suitable for imaging or similar applications.In fine, we aim to combine the photomixer source and the lens in order to attain compact but powerful THz sources.
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| 47. |
- Banik, Biddut Kumar, 1978, et al.
(author)
-
Microwave S-parameter Characterization of an Antenna-Coupled Catadioptric Lens
- 2009
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In: IEEE Antennas and Wireless Propagation Letters. - 1548-5757 .- 1536-1225. ; 8, s. 1299-1301
-
Journal article (peer-reviewed)abstract
- The focusing property of a bow-tie antenna coupled catadioptric lens is studied experimentally using a vector measurement setup. The results show that the lens-antenna provides short-range focusing. Furthermore, the return loss of the lens-antenna was determined numerically and confirmed experimentally from 1 GHz to 10 GHz. The lens-antenna provides 60% bandwidth (VSWR ≤ 2) centered at 6 GHz. Finally, the lens-antenna was employed to detect and locate buried objects and results are presented.
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| 48. |
- Banik, Biddut Kumar, 1978, et al.
(author)
-
Millimeter Wave Characterization of a Catadioptric Lens for Imaging Applications
- 2009
-
In: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 19:11, s. 680-682
-
Journal article (peer-reviewed)abstract
- Characterization of a catadioptric dielectric lens-horn configuration for short-range sensing and imaging is presented. The focusing property is investigated both numerically and experimentally at 108 GHz. The lens-horn provides a focal spot of ~ 0.9λ at a distance of ~ 4.5λ. An imaging example employing the lens in a CW imaging setup is presented. A test pattern was imaged and a marked improvement in image resolution was observed. With the aid of the lens, features close to the wavelength are resolved, which are absent or indistinguishable otherwise.
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| 49. |
- Banik, Biddut Kumar, 1978, et al.
(author)
-
Optimization of the UTC-PD Epitaxy for Photomixing at 340 GHz
- 2008
-
In: International Journal of Infrared and Millimeter Waves. - : Springer Science and Business Media LLC. - 0195-9271 .- 1572-9559. ; 29:10, s. 914-923
-
Journal article (peer-reviewed)abstract
- We present a method to optimize the epitaxial layer structure of an InGaAs/InP uni-traveling-carrier photo-diode (UTC-PD) for continuous THz-wave generation. The design approach used is general in that it can be applied for any target frequency while this study focuses on 340 GHz. The photodiode epitaxy is modeled and optimized using a TCAD software implementing the hydrodynamic semiconductor equations. This physical device model was found to be in good agreement with reported experimental results. It is shown that the UTC-PD can generate ~1 mW at 340 GHz by choosing the optimum absorption layer and collection layer thicknesses.
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| 50. |
- Barrientos, C. Z., et al.
(author)
-
Vertically illuminated TW-UTC photodiodes for terahertz generation
- 2010
-
In: 21st International Symposium on Space Terahertz Technology 2010, ISSTT 2010; Oxford; United Kingdom; 23 March 2010 through 25 March 2010. - 9781617823626 ; , s. 405-408
-
Conference paper (peer-reviewed)abstract
- More efficient continuous-wave photonic nearinfrared mixers as terahertz sources are investigated with the motivation to develop a universal photonic local oscillator for astronomical submillimeter/terahertz receiver systems. For this, our group has developed new concepts for vertically illuminated traveling-wave (TW) photomixers. The new device called TWUni- Travelling Carrier photodiodes (TW-UTC PD) was simulated, modeled and shall be optical/terahertz tested at the Electrical Engineering Department of the University of Chile, whereas device fabrication is performed at the MC2 cleanroom facility at Chalmers University of technology. We are reporting on first progresses in this direction.
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