| 1. |
- Andersson, Kristoffer, 1976, et al.
(författare)
-
Fabrication and characterization of field-plated buried-gate SiC MESFETs
- 2006
-
Ingår i: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 27:7, s. 573-575
-
Tidskriftsartikel (refereegranskat)abstract
- Silicon carbide (SiC) MESFETs were fabricated using a standard SiC MESFET structure with the application of the "buried-channel" and field-plate (FP) techniques in the process. FPs combined with a buried-gate are shown to be favorable concerning output power density and power-added efficiency (PAE), due to higher breakdown voltage and decreased output conductance. A very high power density of 7.8 W/mm was measured on-wafer at 3 GHz for a two-finger 400-/spl mu/m gate periphery SiC MESFET. The PAE for this device was 70% at class AB bias. Two-tone measurements at 3 GHz /spl plusmn/ 100 kHz indicate an optimum FP length for high linearity operation.
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| 2. |
- Nilsson, Per-Åke, 1964, et al.
(författare)
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Influence of Field Plates and Surface Traps on Microwave Silicon Carbide MESFETs
- 2008
-
Ingår i: IEEE Transactions on Electron Devices. - 1557-9646 .- 0018-9383. ; 55:8, s. 1875-1879
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of field plates and surface traps on silicon carbide MESFETs for microwave operation was investigated. By increasing the length of gate-connected field plates from 50 to 800 nm, it was possible to increase the gate–drain breakdown voltage of the devices from 125 to 170 V. At the same time, the current slump effect of traps in the passivation oxide was reduced. By using a combination of field plates and a passivation oxide with low interface trap density, it was possible to reach an output power density of 8 W/mm at 3 GHz.
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| 3. |
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| 4. |
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| 5. |
- Sudow, Mattias, 1980, et al.
(författare)
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An AlGaN/GaN HEMT-Based Microstrip MMIC Process for Advanced Transceiver Design
- 2008
-
Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 56:8, s. 1827-1833
-
Tidskriftsartikel (refereegranskat)abstract
- A MMIC process in AlGaN/GaN technology for advanced transceiver design has been developed. The process is based on microstrip technology with a complete model library of passive elements and AlGaN/GaN HEMTs. The transistor technology in this process is suitable for both power and low noise design, demonstrated with a power density of 5 W/mm, and an ${rm NF}_{min}$ of 1.4 dB at $X$ -band. Process stability of subcircuits, complementary to power amplifiers and LNAs, in a transceiver system have been investigated. The results indicate that an all AlGaN/GaN MMIC transceiver is realizable using this technology.
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| 6. |
- Sudow, Mattias, 1980, et al.
(författare)
-
An SiC MESFET-based MMIC process
- 2006
-
Ingår i: IEEE Transactions on Microwave Theory and Techniques. ; 54:12, Part 1, s. 4072-4078
-
Tidskriftsartikel (refereegranskat)abstract
- A monolithic microwave integrated circuit (MMIC)process based on an in-house SiC MESFET technology has been developed. The process uses microstrip technology, and a complete set of passive components, including MIMcapacitors, spiral inductors,thin-film resistors, and via-holes, has been developed. The potential of the process is demonstrated by an 8-W power amplifierat 3 GHz, a high-linearity -band mixer showing a third-order intercept point of 38 dBm, and a high-power limiter.
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| 7. |
- Sudow, Mattias, 1980, et al.
(författare)
-
The Chalmers microstrip SiC MMIC Process
- 2005
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Ingår i: Conference Proceedings Gighahertz 2005.
-
Konferensbidrag (refereegranskat)abstract
- A generic microstrip MMIC process targeted for SiC and GaN technology has beendeveloped. Passive components for high power operation were developed and verified. Circuit modelsfor both passive and active components have been formulated. Using the developed MMIC process anamplifier and a limiter have been manufactured.
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| 8. |
- Andersson, Christer, 1982, et al.
(författare)
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Epitaxial and Layout Optimization of SiC Microwave Power Varactors
- 2011
-
Ingår i: Asia-Pacific Microwave Conference Proceedings, APMC (APMC 2011 ;Melbourne, VIC; 5 - 8 December 2011). - 9780858259744 ; , s. 1642-1645
-
Konferensbidrag (refereegranskat)abstract
- SiC Schottky diode varactors have been designed for use in tunable microwave power circuits. Epitaxial growth results show excellent material uniformity with low access layer sheet resistances. Two types of device layouts have been evaluated. Island type layouts reduce the parasitic series resistance by 50-60% compared to typical finger layouts. The Q-factors of downscaled island devices are approaching the intrinsic material performance, but are limited by an increasing parasitic parallel capacitance.
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| 9. |
- Axelsson, Olle, 1986, et al.
(författare)
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Impact of Trapping Effects on the Recovery Time of GaN Based Low Noise
- 2016
-
Ingår i: IEEE Microwave and Wireless Components Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-1764 .- 1531-1309. ; 26:1, s. 31-33
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigates recovery time of the gain of AlGaN/GaN HEMT based low noise amplifiers (LNA) after an input overdrive pulse. Three LNAs, fabricated in two commercial MMIC processes and a Chalmers in-house process, are evaluated. The Chalmers process has an unintentionally doped buffer instead of the intentional Fe doping of the buffer which is standard in commercial GaN HEMT technologies. It is shown that the LNAs from the two commercial processes experience a severe drop in gain after input overdrive pulses higher than 28 dBm, recovering over a duration of around 20 ms. In contrast the LNA fabricated in-house at Chalmers experienced no visible effects up to an input power of 33 dBm. These results have impact for radar and electronic warfare receivers, which need to be operational immediately after an overdrive pulse. The long time constants suggest that these effects are due to trapping in the transistors with the Fe doped buffer playing an important role.
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| 10. |
- Billström, Niklas, et al.
(författare)
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High performance GaN front-end MMICs
- 2011
-
Ingår i: 14th European Microwave Week 2011: "Wave to the Future", EuMW 2011 - 6th European Microwave Integrated Circuit Conference, EuMIC 2011, Manchester, 10 October through 11 October 2011. - 9782874870231 ; , s. 348-351
-
Konferensbidrag (refereegranskat)
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| 11. |
- Chehrenegar, Pirooz, 1964, et al.
(författare)
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Design and characterization of a highly linear 3 GHz GaN HEMT amplifier
- 2011
-
Ingår i: 2011 Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits, INMMiC 2011. Vienna, 18-19 April 2011. - 9781457706493
-
Konferensbidrag (refereegranskat)abstract
- In this paper a highly linear amplifier using an in-house gallium nitride (GaN) high electron mobility transistor (HEMT) technology is presented. A 3 dB bandwidth of 2.7-3.6 GHz with a maximum gain of 18 dB was measured. The output third-order intercept point (OIP3) was measured to 39 dBm with a maximum power consumption of 2.1 W. With a reduction of power consumption to 1 W the noise figure was improved by 0.6 dB while the OIP3 was degraded 3 dB.
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| 12. |
- Divinyi, Andreas, et al.
(författare)
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Transition Time of GaN HEMT Switches and its Dependence on Device Geometry
- 2023
-
Ingår i: 2023 18th European Microwave Integrated Circuits Conference, EuMIC 2023. ; , s. 46-49
-
Konferensbidrag (refereegranskat)abstract
- This paper presents the impact on the slow transition time of GaN HEMT switch transistor due to size and geometry. Measurements in the time domain are used to characterize the transition time of the switch from off to on. This is done for several switch transistors with variations on total gate width and number of fingers. In order to enable the comparison of transition times a figure of merit is established. This is achieved by using a commonly used model for trapping effects to quantify the amplitude of the slow transient with respect to the gate voltage. The resulting analysis indicates that transition time is sensitive to transistor size and dependent on the geometry of the device as increasing the width of the gate fingers is more advantageous compared to increasing the number of fingers.
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| 13. |
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| 14. |
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| 15. |
- Fagerlind, Martin, 1980, et al.
(författare)
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Investigation of the interface between silicon nitride passivations and AlGaN/AlN/GaN heterostructures by C(V) characterization of metal-insulator-semiconductor-heterostructure capacitors
- 2010
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 108:1
-
Tidskriftsartikel (refereegranskat)abstract
- Capacitance-voltage [C(V)] measurements of metal-insulator-semiconductor-heterostructure capacitors are used to investigate the interface between silicon nitride passivation and AlGaN/AlN/GaN heterostructure material. AlGaN/AlN/GaN samples having different silicon nitride passivating layers, deposited using three different deposition techniques, are evaluated. Different interface state distributions result in large differences in the C(V) characteristics. A method to extract fixed charge as well as traps from the C(V) characteristics is presented. Rough estimates of the emission time constants of the traps can be extracted by careful analysis of the C(V) characteristics. The fixed charge is positive for all samples, with a density varying between 1.3 x 10(12) and 7.1 x 10(12) cm(-2). For the traps, the peak density of interface states is varying between 16 x 10(12) and 31 x 10(12) cm(-2) eV(-1) for the three samples. It is concluded that, of the deposition methods investigated in this report, the low pressure chemical vapor deposited silicon nitride passivation shows the most promising results with regards to low densities of interface states. (C) 2010 American Institute of Physics. [doi:10.1063/1.3428442]
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| 16. |
- Hjelmgren, Hans, 1960, et al.
(författare)
-
Electro-thermal simulations of a microwave 4H-SiC MESFET on high purity semi-insulating substrate
- 2007
-
Ingår i: Solid-State Electronics. - : Elsevier BV. - 0038-1101. ; 51:8, s. 1144-1152
-
Tidskriftsartikel (refereegranskat)abstract
- DC and small-signal electro-thermal simulations of a 4H-SiC microwave power MESFET on a high purity semi-insulating substrate are compared to measurements. The focus is on the electron transport, substrate traps, and thermal heating. The doping concentrations are described by measured SIMS profiles, and the material parameters are in accordance with published results. Although the simulated MESFET has a p-buffer and a high purity substrate, the simulations show that the density of shallow traps affects the device characteristics.The very good agreement between simulated and measured DC and small-signal characteristics indicates that the models for electron mobility, substrate traps, and heating are the most important to achieve good agreement with measured data.
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| 17. |
- Hjelmgren, Hans, 1960, et al.
(författare)
-
Transient Simulation of Microwave SiC MESFETs With Improved Trap Models
- 2010
-
Ingår i: IEEE Transactions on Electron Devices. - 1557-9646 .- 0018-9383. ; 57:3, s. 729-732
-
Tidskriftsartikel (refereegranskat)abstract
- Measured and simulated transient characteristics ofa SiC metal–semiconductor field-effect transistor are compared. Self-heating, gate tunneling, substrate, and surface traps are taken into account in the simulations. By explicitly filling surface traps at the vicinity of the gate during pinchoff, close correspondence between simulated and measured gate lags is achieved.
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| 18. |
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| 19. |
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| 20. |
- Nilsson, Joakim, et al.
(författare)
-
S-band discrete and MMIC GaN power amplifiers
- 2009
-
Ingår i: European Microwave Week 2009, EuMW 2009: Science, Progress and Quality at Radiofrequencies, Conference Proceedings - 39th European Microwave Conference, EuMC 2009. - 9782874870125 ; , s. 495-498
-
Konferensbidrag (refereegranskat)abstract
- The use of GaN devices for microwave power amplifiers begins to be a reality in Europe. This paper describes two S-band (2.7-3.3 GHz) high power amplifier (HPA) designs; one discrete 100 W output stage and one 10 W MMIC power amplifier. The discrete power amplifier is designed using two GaN power bars with a total gate width of 19.2 mm. The GaN power bars have been developed by Selex-SI, within the european co-project Korrigan. The MMIC power amplifier was designed using a 0.25 ?m GaN HEMT process supplied and processed by Chalmers.
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| 21. |
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| 22. |
- Sudow, Mattias, 1980, et al.
(författare)
-
A highly linear double balanced Schottky diode S-band mixer
- 2006
-
Ingår i: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 16:6, s. 336 - 8
-
Tidskriftsartikel (refereegranskat)abstract
- A high-level double balanced SiC Schottky diode mixer in SiC monolithic microwave integrated circuit (MMIC) technology has been designed, processed and characterized. The mixer is a single ended in- and output circuit with coupled transformers as baluns to enable a compact design, resulting in a total area of 2.2×2.2mm2. The mixer has a maximum IIP3 of 38dBm and IIP2 of 58dBm at 3.3GHz, and a typical P1 dB of 23dBm in the S-band. The minimum conversion loss was 12dBm at 2.4GHz. The high power operation of the mixer shows that SiC MMIC can perform well in high microwave radiation environments
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| 23. |
- Sudow, Mattias, 1980, et al.
(författare)
-
A Single-Ended Resistive $X$-Band AlGaN/GaN HEMT MMIC Mixer
- 2008
-
Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 56:10, s. 2201-2206
-
Tidskriftsartikel (refereegranskat)abstract
- A broadband highly linear X-band mixer in AlGaN/GaN monolithic microwave integrated circuit technology has been designed, processed, and characterized. The design is based on a 4 times 100 mum AlGaN/GaN HEMT in a single-ended circuit topology. The mixer has an IF bandwidth of 2 GHz with a conversion loss (CL) of
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| 24. |
- Sudow, Mattias, 1980, et al.
(författare)
-
Planar Schottky Microwave Diodes on 4H-SiC
- 2005
-
Ingår i: Materials Science Forum. - 1662-9752 .- 0255-5476. ; 483-485, s. 937-940
-
Konferensbidrag (refereegranskat)abstract
- Planar microwave Schottky diodes on 4H-SiC have been designed, processed and measured. Different Schottky metals were tested to study the influence on the microwave performance. A maximum extrinsic cut-off frequency of 30.8 GHz was achieved for a tungsten/SiC-Schottky diode. The diode geometry dependence on both the cut-off frequency and the breakdown voltage was investigated. The breakdown voltage was found to be linearly dependent on the anode-cathode distance
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| 25. |
- Sudow, Mattias, 1980, et al.
(författare)
-
Planar SiC Schottky Diodes for MMIC Applications
- 2004
-
Ingår i: Conference Proceedings. 34th European Microwave Conference (IEEE Cat. No.04EX963). ; 1, s. 153-156
-
Tidskriftsartikel (refereegranskat)abstract
- Planar Schottky diodes intended for SiC MMIC applications have been designed, processed and characterised. To our knowledge, this is the first article published on this type of device. The planar design is beneficial since semi-insulating substrates are used in microwave designs to minimise parasitics. The component geometry was studied and a simple distributed model was formulated. Extrinsic cut-off frequencies up to 30.8 GHz were calculated from LCR-measurements.
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| 26. |
- Sudow, Mattias, 1980, et al.
(författare)
-
SiC varactors for dynamic load modulation of high power amplifiers
- 2008
-
Ingår i: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 29:7, s. 728-730
-
Tidskriftsartikel (refereegranskat)abstract
- SiC Schottky diode varactors with a high breakdown voltage, a high tuning ratio, and a low series resistance have been designed and fabricated. These characteristics are particularly necessary for the dynamic load modulation of high power amplifiers (PAs), which is an attractive alternative to other efficiency enhancement techniques. For a SiC Schottky diode varactor with a 50-µm radius fabricated by using a graded doping profile, a breakdown voltage of 40 V, a tuning range of 5.6, and a series resistance of 0.9 O were achieved. The results show the great potential of this type of varactors for the use in the dynamic load modulation of high power amplifiers. © 2008 IEEE.
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| 27. |
- Thorsell, Mattias, 1982, et al.
(författare)
-
An X-Band AlGaN/GaN MMIC Receiver Front-End
- 2010
-
Ingår i: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 20:1, s. 55-57
-
Tidskriftsartikel (refereegranskat)abstract
- This letter presents an integrated AlGaN/GaN X-band receiver front-end. This is to the authors knowledge the first published results of an integrated AlGaN/GaN MMIC receiver front-end. The receiver uses an integrated SPDT switch to reduce size, weight and cost compared to circulator based transceiver front-ends. The integrated front-end has more than 13 dB of gain and a noise figure of 3.5 dB at 11 GHz.
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| 28. |
- Thorsell, Mattias, 1982, et al.
(författare)
-
Characterization of the temperature dependent access resistances in AlGaN/GaN HEMTs
- 2008
-
Ingår i: Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits, 2008. INMMIC 2008.. - 9781424426454 ; , s. 17-20
-
Konferensbidrag (refereegranskat)abstract
- The temperature dependence of the access resistances for AlGaN/GaN HEMTs is investigated. The self-heating is measured using infrared microscopy and the access resistances are extracted at different ambient temperatures. Their influence on the intrinsic small signal parameters is studied versus bias and ambient temperature.
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| 29. |
- Thorsell, Mattias, 1982, et al.
(författare)
-
Thermal characterization of the intrinsic noise parameters for AlGaN/GaN HEMTs
- 2008
-
Ingår i: International Microwave Symposium Digest, 2008, Atlanta. - 0149-645X. - 9781424417810 ; , s. 463-466
-
Konferensbidrag (refereegranskat)abstract
- The noise parameters of AlGaN/GaN-HEMTs are measured between 298 K and 423 K. The temperature dependent access resistances are de-embedded and the intrinsic noise parameters are studied as a function of temperature. It is shown that the parasitic access resistances are limiting the highfrequency noise performance of the AlGaN/GaN-HEMT.The intrinsic noise sources are extracted and a noise model is derived and verified for a MMIC amplifier.
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| 30. |
- Thorsell, Mattias, 1982, et al.
(författare)
-
Thermal Study of the High-Frequency Noise in GaN HEMTs
- 2009
-
Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 57:1, s. 19-26
-
Tidskriftsartikel (refereegranskat)abstract
- The high-frequency noise performance of the GaN HEMT is studied for temperatures between 297–398 K. The access resistances ${ R}_{ S}$ and ${ R}_{ D}$ have a limiting effect on the noise performance, and in this paper, their temperature dependence is studied in detail for a ${hbox{2}}times {hbox{100}} mu{hbox{m}}$ GaN HEMT. ${ R}_{ S}$ and ${ R}_{ D}$ show an increase of 0.71 and 0.86 %/K, respectively. The self-heating effect due to dissipated power is also studied to allow accurate intrinsic small-signal and noise parameter extraction. The thermal resistance is measured by infrared microscopy. Based on these results, a temperature dependent noise model including self-heating and temperature-dependent access resistances is derived and verified with measurements.
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| 31. |
- Westlund, Andreas, 1985, et al.
(författare)
-
Graphene self-switching diodes as zero-bias microwave detectors
- 2015
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 106:9, s. 093116-
-
Tidskriftsartikel (refereegranskat)abstract
- Self-switching diodes (SSDs) were fabricated on as-grown and hydrogen-intercalated epitaxial graphene on SiC. The SSDs were characterized as zero-bias detectors with on-wafer measurements from 1 to 67 GHz. The lowest noise-equivalent power (NEP) was observed in SSDs on the hydrogen-intercalated sample, where a flat NEP of 2.2 nW/Hz½ and responsivity of 3.9 V/W were measured across the band. The measured NEP demonstrates the potential of graphene SSDs as zero-bias microwave detectors.
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| 32. |
- Winters, Michael, 1986, et al.
(författare)
-
Hysteresis modeling in graphene field effect transistors
- 2015
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 117:7, s. Art. no, 074501-
-
Tidskriftsartikel (refereegranskat)abstract
- Graphene field effect transistors with an Al2O3 gate dielectric are fabricated on H-intercalated bilayer graphene grown on semi-insulating 4H-SiC by chemical vapour deposition. DC measurements of the gate voltage nu(g) versus the drain current i(d) reveal a severe hysteresis of clockwise orientation. A capacitive model is used to derive the relationship between the applied gate voltage and the Fermi energy. The electron transport equations are then used to calculate the drain current for a given applied gate voltage. The hysteresis in measured data is then modeled via a modified Preisach kernel.
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| 33. |
- Andersson, Christer, 1982, et al.
(författare)
-
A packaged 86 W GaN transmitter with SiC varactor-based dynamic load modulation
- 2013
-
Ingår i: 43rd European Microwave Conference, EuMC 2013 - Held as Part of the 16th European Microwave Week, EuMW 2013, Nuremberg, Germany, 7-10 October 2013. - 9782874870316 ; , s. 283-286
-
Konferensbidrag (refereegranskat)abstract
- Output power scaling based on class-J dynamic load modulation (DLM) theory is used to design an unprecedentedly high power microwave transmitter with varactor-based DLM functionality. Matching networks are realized on high dielectric constant substrates in order to reduce the form factor. The fully matched DLM PA incorporates a 24-mm GaN HEMT powerbar and a stack of four SiC varactors, all fit into a CuW package (40 mm × 20 mm). Peak output power is reconfigurable by changing the drain voltage, while retaining the DLMeffect. Under pulsed conditions at 40 V the PA delivers a peak power of 86 W at 2.14 GHz. Efficiency enhancement by DLM is 10-15 percentage-units at 6 dB output power back-off (OPBO). Employing digital predistortion (DPD) with a vector switched generalized memory polynomial (VS-GMP) the ACLR is -46 dBc at an average output power of 17 W and a drain efficiency of 34%. These results prove the potential for high output power levels in varactor-based DLM transmitters.
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| 34. |
- Andersson, Christer, 1982, et al.
(författare)
-
A SiC Varactor With Large Effective Tuning Range for Microwave Power Applications
- 2011
-
Ingår i: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0741-3106 .- 1558-0563. ; 32:6, s. 788-790
-
Tidskriftsartikel (refereegranskat)abstract
- SiC Schottky diode varactors have been fabricated for use in microwave power applications, specifically the dynamic load modulation of power amplifiers. A custom doping profile has been employed to spread the C(V) over a large bias voltage range, thereby increasing the effective tuning range under large voltage swing conditions. The small-signal tuning range is approximately six, and punch through is reached at a bias voltage of -60 V, while the breakdown voltage is on the order of -160 V. An interdigitated layout is utilized together with a self-aligned Schottky anode etch process to improve the Q-factor at 2 GHz, which is 20 at zero bias and approximately 160 at punch through.
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| 35. |
- Andersson, Christer, 1982, et al.
(författare)
-
Decade bandwidth high efficiency GaN HEMT power amplifier designed with resistive harmonic loading
- 2012
-
Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. - 9781467310871
-
Konferensbidrag (refereegranskat)abstract
- The use of resistive loading at higher harmonics in wideband power amplifier design is proposed. Although the theoretical efficiency of such operation is lower than other classes the significantly simplified load network design potentially allows for multi-octave realizations. A decade bandwidth (0.4-4.1 GHz) GaN HEMT power amplifier was thereby designed, delivering more than 40 dBm output power with 10-15 dB gain and 40-62% drain efficiency. Linearized modulated signal amplification was then successfully demonstrated at multiple frequencies (0.9 to 3.5 GHz), using various downlink signals (LTE, WCDMA, WiMAX), with resulting ACLR lower than 46 dBc.
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| 36. |
- Andersson, Christer, 1982, et al.
(författare)
-
Nonlinear Characterization of Varactors for Tunable Networks by Active Source-Pull and Load-Pull
- 2011
-
Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 59:7, s. 1753-1760
-
Tidskriftsartikel (refereegranskat)abstract
- Varactors are key components in the realization of tunable networks, for instance, in high-efficiency power-amplifier architectures. This paper presents a method to measure the varactor quality factor (Q-factor) in the presence of nonlinear distortion. The importance of correctly choosing the loading condition at the second harmonic is illustrated by multiharmonic active source- and load-pull measurements. Furthermore, the method also allows for accurate extraction of the bias-dependent series resistance without the need of area consuming resonant structures. The proposed method is applied to characterize a silicon-carbide (SiC) Schottky diode varactor at 3 GHz. The measured results reemphasize that varactors are not linear tunable, but inherently nonlinear components that require proper consideration of the higher order harmonics.
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| 37. |
- Andersson, Christer, 1982, et al.
(författare)
-
Theory and Design of Class-J Power Amplifiers With Dynamic Load Modulation
- 2012
-
Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 60:12, s. 3778-3786
-
Tidskriftsartikel (refereegranskat)abstract
- A theory for class-J microwave amplifier operation as a function of drive level and fundamental load impedance is derived. Calculations show that, under appropriate operating conditions, it is sufficient to modulate the transistor load reactance to enable high-efficiency operation (>70%) over a large output power dynamic range (>10 dB) with high transistor power utilization. Such dynamic load modulation (DLM) networks are an ideal application of continuously tunable varactor technologies. Multiharmonic load–pull measurements are performed on a GaN HEMT and experimentally verify the theory of operation. A demonstrator amplifier using an SiC varactor technology is then designed and characterized by static measurements. The amplifier has a peak power of 38 dBm at 2.08 GHz and maintains efficiencies above 45% over 8 dB of power dynamic range. An analysis of the load network losses is performed to show the potential of the class-J DLM transmitter concept.
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| 38. |
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| 39. |
- Andersson, Kristoffer, 1976, et al.
(författare)
-
Resistive SiC-MESFET mixer
- 2002
-
Ingår i: IEEE Microwave and Wireless Components Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1531-1309 .- 1558-1764. ; 12:4, s. 119-121
-
Tidskriftsartikel (refereegranskat)abstract
- A single-ended silicon carbide resisitve MESFET mixer with minimum conversion loss (CL) of 10.2 dB and an input third order intercept point of 35.7 dB at 3.3 GHz was designed and characterized. A lumped-element, large-signal model was used for modeling the device. The drain-source resistance was measured by taking the real part of the output port impedence. Analysis suggested that the optimum gate bias for minimum CL was -6.7 V.
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| 40. |
- Angelov, Iltcho, 1943, et al.
(författare)
-
A balanced millimeter wave doubler based on pseudomorphic HEMTs
- 1992
-
Ingår i: 1992 IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. ; 1, s. 353-356
-
Konferensbidrag (refereegranskat)abstract
- A balanced HEMT (high electron mobility transistor) doubler for operation at millimeter waves has been analyzed, fabricated, and characterized. Particular attention has been paid to the influence of the output circuit on the performance of the doubler. The doubler was analyzed with a harmonic balance method and an output power of 4 dBm at 42 GHz was obtained experimentally. The conversion gain is approximately -1 dB at 40 GHz at an input power of 5 dBm. Bias and frequency response were very close to the predicted ones.
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| 41. |
- Angelov, Iltcho, 1943, et al.
(författare)
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A new empirical nonlinear model for HEMT-devices
- 1992
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Ingår i: 1992 IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. - 0780306112 ; 3, s. 1583-1586
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Konferensbidrag (refereegranskat)abstract
- A novel signal model for HEMTs (high-electron-mobility transistors) capable of modeling the current-voltage characteristic and its derivatives, including the characteristic transconductance peak and gate-source and gate-drain capacitances, is described. Model parameter extraction is straightforward and is performed for a submicron gate-length ∂-doped pseudomorphic HEMT. The model has been used to predict the DC- and S-parameters of the devices and different nonlinear circuits such as mixers and multipliers with very high accuracy.
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| 42. |
- Angelov, Iltcho, 1943, et al.
(författare)
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F-band resistive mixer based on heterostructure field effect transistor technology
- 1993
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Ingår i: Proceedings of the 1993 IEEE MTT-S International Symposium on Circuits and Systems. - 0149-645X. - 0780312090 ; 2, s. 787-790
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Konferensbidrag (refereegranskat)abstract
- A fundamentally pumped millimeter wave resistive mixer based on an HFET technology working at F-band (90-140 GHz) is described for the first time. Nonlinear simulations have been performed for this mixer based on an specially designed double δ-doped pseudomorphic HFET device developed for this application. A minimum conversion loss between 12 to 13 dB was measured with the RF fixed at different frequencies between 108 to 114 GHz at an RF power of -13 dBm. Both theoretical and experimental results are presented in this paper.
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| 43. |
- Angelov, Iltcho, 1943, et al.
(författare)
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Large-Signal Modelling and Comparison of AlGaN/GaN HEMTs and SiC MESFETs
- 2006
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Ingår i: IEEE Asia PAcific Microwave Conference, 2006, Yokohama, Japan. - 9784902339116 ; , s. 279-282
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Konferensbidrag (refereegranskat)abstract
- The Large Signal (LS) model for GaN and SiC FET devices was developed and evaluated with DC, S, and LS measurements. Special attention was paid to improve the management of harmonics and provide. a more physical treatment of the dispersion. The model was implemented in a commercial CAD tool and exhibit good overall accuracy.
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| 44. |
- Angelov, Iltcho, 1943, et al.
(författare)
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On the delay implementation in FET Large Signal Models
- 2020
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Ingår i: 2020 International Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits, INMMiC 2020 - Proceedings. - 9781728126456
-
Konferensbidrag (refereegranskat)abstract
- Several options for implementing FET channel delay in user defined Large Signal models (LS) are discussed. The high importance of precise definition of reference planes for MMIC operating in mm waves is discussed as well. The delay implementation and a way to improve the reference planes accuracy was tested in a special two stage W-band test amplifier circuit. The LS model was used later to design several practical MMIC circuits.
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| 45. |
- Angelov, Iltcho, 1943, et al.
(författare)
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On the large-signal modeling of High Power AlGaN/GaN HEMTs
- 2012
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Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. - 9781467310871
-
Konferensbidrag (refereegranskat)abstract
- In this paper are given some recent results on modeling of High Power GaN HEMT devices. The GaN HEMT is very promising for high power application, but we push device to the limits, so many issues are becoming critical. For example, access resistances Rs, Rd in high power GAN HEMT are bias and temperature dependent-their extraction from cold FET measurements can lead to over optimistic prediction for output power. Thermal management, self-heating modeling are another very important issue-they influence reliability, power and PAE. Models without dynamic self-heating are not practical for GaN. The models without breakdown can easily predict world records for PAE, output power/mm etc. Some examples are given using vectorial Large Signal Measurements (LSNA/NVNA) to provide useful, global info about device behavior, influence of traps, knee voltage walkout etc.
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| 46. |
- Axelsson, Olle, 1986, et al.
(författare)
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Application Relevant Evaluation of Trapping Effects in AlGaN/GaN HEMTs With Fe-Doped Buffer
- 2016
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Ingår i: IEEE Transactions on Electron Devices. - 1557-9646 .- 0018-9383. ; 63:1, s. 326-332
-
Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the impact of different iron (Fe) buffer doping profiles on trapping effects in microwave AlGaN/gallium nitride (GaN) high electron mobility transistors (HEMTs). We characterize not only the current collapse due to trapping in the buffer, but also the recovery process, which is important in the analysis of suitable linearization schemes for amplitude modulated signals. It is shown that the simple pulsed dc measurements of current transients can be used to investigate transient effects in the RF power. Specifically, it is revealed that the design of the Fe-doping profile in the buffer greatly influences the recovery time, with the samples with lower Fe concentration showing slower recovery. In contrast, traditional indicators, such as S-parameters and dc as well as pulsed $I$-$V$ characteristics, show very small differences. An analysis of the recovery shows that this effect is due to the presence of two different detrapping processes with the same activation energy (0.6 eV) but different time constants. For highly doped buffers, the faster process dominates, whereas the slower process is enhanced for less doped buffers.
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| 47. |
- Axelsson, Olle, 1986, et al.
(författare)
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The Effect of Forward Gate Bias Stress on the Noise Performance of Mesa Isolated GaN HEMTs
- 2015
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Ingår i: IEEE Transactions on Device and Materials Reliability. - : Institute of Electrical and Electronics Engineers (IEEE). - 1530-4388 .- 1558-2574. ; 15:1, s. 40-46
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates degradation of gallium nitride (GaN) high-electron mobility transistor (HEMT) noise performance after both dc and RF stress with forward gate current. The results are used to facilitate optimization of the robustness of GaN low-noise amplifiers (LNAs). It is shown that forward biasing the gate of a GaN HEMT results in permanent degradation of noise performance and gate current leakage, without affecting S-parameters and drain current characteristics. The limit of safe operation of the 2 x 50 mu m devices in this study is found to be between 10 and 20 mW dissipated in the gate diode for both dc and RF stress. We propose that degradation could be caused by excessive leakage through the mesa sidewalls at the edges of each gate finger. Circuit simulations may be used together with device robustness rating to optimize LNAs for maximum input power tolerance. Using a resistance in the gate biasing network of 10 k Omega, it is estimated that an LNA utilizing a 2 x 50 mu m device could withstand input power levels up to 33 dBm without degradation in noise performance.
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| 48. |
- Bergsten, Johan, 1988, et al.
(författare)
-
AlGaN/GaN high electron mobility transistors with intentionally doped GaN buffer using propane as carbon precursor
- 2016
-
Ingår i: Japanese Journal of Applied Physics. - : IOP Publishing. - 1347-4065 .- 0021-4922. ; 55:5
-
Tidskriftsartikel (refereegranskat)abstract
- AlGaN/GaN high electron mobility transistors (HEMTs) fabricated on a heterostructure grown by metalorganic chemical vapor deposition using an alternative method of carbon (C) doping the buffer are characterized. C-doping is achieved by using propane as precursor, as compared to tuning the growth process parameters to control C-incorporation from the gallium precursor. This approach allows for optimization of the GaN growth conditions without compromising material quality to achieve semi-insulating properties. The HEMTs are evaluated in terms of isolation and dispersion. Good isolation with OFF-state currents of 2 x 10(-6)A/mu m, breakdown fields of 70V/mu m, and low drain induced barrier lowering of 0.13mV/V are found. Dispersive effects are examined using pulsed current-voltage measurements. Current collapse and knee walkout effects limit the maximum output power to 1.3W/mm. With further optimization of the C-doping profile and GaN material quality this method should offer a versatile approach to decrease dispersive effects in GaN HEMTs. (C) 2016 The Japan Society of Applied Physics
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| 49. |
- Bergsten, Johan, 1988, et al.
(författare)
-
Electron Trapping in Extended Defects in Microwave AlGaN/GaN HEMTs with Carbon-Doped Buffers
- 2018
-
Ingår i: IEEE Transactions on Electron Devices. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1557-9646 .- 0018-9383. ; 65:6, s. 2446-2453
-
Tidskriftsartikel (refereegranskat)abstract
- This paper investigates AlGaN/GaN high-electron mobility transistors (HEMTs) fabricated on epistructures with carbon (C)-doped buffers. Metalorganic chemical vapor deposition is used to grow two C-doped structures with different doping profiles, using growth parameters to change the C incorporation. The C concentration is low enough to result in n-type GaN. Reference devices are also fabricated on a structure using iron (Fe) as dopant, to exclude any process related variations and provide a relevant benchmark. All devices exhibit similar dc performance. However, pulsed I - V$ measurements show extensive dispersion in the C-doped devices, with values of dynamic R-mathrm-scriptscriptstyle ON 3 -4 times larger than in the dc case. Due to the extensive trapping, the devices with C-doped buffers can only supply about half the output power of the Fe-doped sample, 2.5 W/mm compared to 4.8 W/mm at 10 GHz. In drain current transient measurements, the trap filling time is varied, finding large prevalence of trapping at dislocations for the C-doped samples. Clusters of C around the dislocations are suggested to be the main cause for the increased dispersion.
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| 50. |
- Bergsten, Johan, 1988, et al.
(författare)
-
Low resistive Au-free, Ta-based, recessed ohmic contacts to InAlN/AlN/GaN heterostructures
- 2015
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Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 1361-6641 .- 0268-1242. ; 30:10, s. 105034-
-
Tidskriftsartikel (refereegranskat)abstract
- The formation of recess etched Au-free ohmic contacts to an InAlN/AlN/GaN heterostructure is investigated. A Ta/Al/Ta metal stack is used to produce contacts with contact resistance (R-c) as low as 0.14 Omega mm. It is found that R-c decreases with increasing recess depth until the InAlN barrier is completely removed. For even deeper recesses R-c remains low but requires annealing at higher temperatures for contact formation. The lowest R-c is found for contacts where the recess etch has stopped just above the 2D electron gas channel. At this depth the contacts are also found to be less sensitive to other process parameters, such as anneal duration and temperature. An optimum bottom Ta layer thickness of 5-10 nm is found. Two reliability experiments preliminary confirm the stability of the recessed contacts.
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