| 1. |
- Andersson, Kristoffer, 1976, et al.
(författare)
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Fabrication and characterization of field-plated buried-gate SiC MESFETs
- 2006
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Ingår i: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 27:7, s. 573-575
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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
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Ingår i: IEEE Transactions on Electron Devices. - 1557-9646 .- 0018-9383. ; 55:8, s. 1875-1879
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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
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 56:8, s. 1827-1833
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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)
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An SiC MESFET-based MMIC process
- 2006
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. ; 54:12, Part 1, s. 4072-4078
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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)
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The Chalmers microstrip SiC MMIC Process
- 2005
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Ingår i: Conference Proceedings Gighahertz 2005.
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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. |
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| 9. |
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| 10. |
- Hjelmgren, Hans, 1960, et al.
(författare)
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Electro-thermal simulations of a microwave 4H-SiC MESFET on high purity semi-insulating substrate
- 2007
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Ingår i: Solid-State Electronics. - : Elsevier BV. - 0038-1101. ; 51:8, s. 1144-1152
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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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| 11. |
- Nilsson, Joakim, et al.
(författare)
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S-band discrete and MMIC GaN power amplifiers
- 2009
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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
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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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| 12. |
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| 13. |
- Sudow, Mattias, 1980, et al.
(författare)
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A highly linear double balanced Schottky diode S-band mixer
- 2006
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Ingår i: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 16:6, s. 336 - 8
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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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| 14. |
- Sudow, Mattias, 1980, et al.
(författare)
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A Single-Ended Resistive $X$-Band AlGaN/GaN HEMT MMIC Mixer
- 2008
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 56:10, s. 2201-2206
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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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| 15. |
- Sudow, Mattias, 1980, et al.
(författare)
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Planar Schottky Microwave Diodes on 4H-SiC
- 2005
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Ingår i: Materials Science Forum. - 1662-9752 .- 0255-5476. ; 483-485, s. 937-940
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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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| 16. |
- Sudow, Mattias, 1980, et al.
(författare)
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SiC varactors for dynamic load modulation of high power amplifiers
- 2008
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Ingår i: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 29:7, s. 728-730
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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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| 17. |
- Thorsell, Mattias, 1982, et al.
(författare)
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Characterization of the temperature dependent access resistances in AlGaN/GaN HEMTs
- 2008
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Ingår i: Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits, 2008. INMMIC 2008.. - 9781424426454 ; , s. 17-20
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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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| 18. |
- Thorsell, Mattias, 1982, et al.
(författare)
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Thermal characterization of the intrinsic noise parameters for AlGaN/GaN HEMTs
- 2008
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Ingår i: International Microwave Symposium Digest, 2008, Atlanta. - 0149-645X. - 9781424417810 ; , s. 463-466
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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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| 19. |
- Thorsell, Mattias, 1982, et al.
(författare)
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Thermal Study of the High-Frequency Noise in GaN HEMTs
- 2009
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 57:1, s. 19-26
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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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| 20. |
- 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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| 21. |
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| 22. |
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| 23. |
- Desmaris, Vincent, 1977, et al.
(författare)
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Influence of oxynitride (SiOxNy) passivation on the microwave performance of AlGaN/GaN HEMTs
- 2008
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Ingår i: Solid-State Electronics. ; 52, s. 632-636
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Tidskriftsartikel (refereegranskat)abstract
- The effects of the composition of oxynitride passivations (SiOxNy) deposited by plasma enhanced chemical-vapor deposition (PECVD) at room temperature on the microwave performance of AlGaN/GaN high electron mobility transistors (HEMTs) were investigated. Five different SiOxNy passivating layers were deposited covering the whole range of dielectrics combinations from SiOx to SiNy. Their impacts on the HEMT performance were studied by means of DC, S-parameters, pulsed IV and load-pull measurements. The oxynitride dielectric with a refraction index of 1.58 was shown to be an effective SiOxNy passivation for limiting the gate-lag effects in the HEMTs and at the same time increasing the breakdown voltage of the device. It is thus a promising passivation layer for microwave power high voltage and high power applications.
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| 24. |
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| 25. |
- Fagerlind, Martin, 1980, et al.
(författare)
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A room temperature HEMT process for AlGaN/GaN heterostructure characterization
- 2009
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Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 1361-6641 .- 0268-1242. ; 24:4, s. 045014-
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Tidskriftsartikel (refereegranskat)abstract
- A simple, room temperature, AlGaN/GaN high electron mobility transistor (HEMT) process is presented. The process consists of only two steps which can be performed by hand. The first step is to deposit gallium (Ga) metal for ohmic contacts, which without thermal processing have a specific contact resistivity ρ_c=0.10 Ohm cm2. Silver (Ag)-based conductive paint is then deposited to form a Schottky contact. The simplicity of the process facilitates fast fabrication and characterization of HEMTs, without unwanted effects on the material. The process is useful for initial material characterization and screening. The process is also found to be a useful tool for process monitoring of the conventional HEMT micro-fabrication process by detecting material/process quality problems. In this work the process is used for initial material characterization and screening, where a leaky buffer can easily be detected. The process is also used to identify the ohmic contact annealing as a potentially damaging step in a conventional micro-fabrication process. A decrease in the electron sheet carrier concentration and an increase of leakage currents are measured after annealing.
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| 26. |
- Fagerlind, Martin, 1980, et al.
(författare)
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Influence of gate position on dispersion characteristics of GaN HEMTs
- 2008
-
Ingår i: WOCSDICE 2008, Abstract book. ; , s. 99-100
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Konferensbidrag (refereegranskat)abstract
- GAN HEMTs with varying design have been fabricated to optimize device performance. The focus of this report is the minimization of drain current dispersion by the variation of the electric field distribution. In this work this is done by varying the placement of the gate and to some extent varying gate length and length of the gate connected field plate. We present pulsed IV characteristics for a number of different device designs.
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| 27. |
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| 28. |
- Shiu, Jin-Yu, 1978, et al.
(författare)
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Comparison of the DC and microwave performance of AlGaN/GaN HEMTs with sputter PVD or plasma enhanced CVD grown silicon nitride (SiNx) passivation layer
- 2006
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Ingår i: WOCSDICE 2006 Proceedings, Fiskebäckskil 2006.
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Konferensbidrag (refereegranskat)abstract
- Sputter and plasma enhanced chemical vapor deposition (PECVD) processed SiNx passivation layer on AlGaN/GaN high electron mobility transistors (HEMTs) was compared in this investigation. The both samples were process on the same wafer and the same process besides the passivation process in the same batch. From the data of DC, mimicked class B quiescent bias point pulse measurement, transient pulse measurement are showing that the sputter passivation HEMTs have better performance because there are fewer surface traps. The power sweep data from load pull measurement were in accordance with the pulsed measurement data. Without cooling, continuous wave power densities of 4W/mm and 3.1W/mm was measured at 3GHz on the sputter and PECVD passivation HEMTs, respectively.
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| 29. |
- Shiu, Jin-Yu, 1978, et al.
(författare)
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DC and microwave performance of AlGaN/GaN HEMTs passivated with sputtered SiNx
- 2007
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Ingår i: Semicronductor Science and Technology. ; 22, s. 717-721
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Tidskriftsartikel (refereegranskat)abstract
- The effects of sputtered and room temperature plasma enhanced chemical vapour deposition (RT-PECVD) SiNx passivation on the dc and microwave performance of AlGaN/GaN high electron mobility transistors (HEMTs)are studied. The pulsed I–V characteristics from a class B quiescent bias point and transient measurements indicate that the sputtered SiNx passivation is more efficient in suppressing lag effects in AlGaN/GaN HEMTs. Dispersion-free sputtered SiNx passivated AlGaN/GaN HEMTs were obtained using this technique. Continuous-wave (CW) measurements without active cooling give a maximum output power density of 6.6 W mm−1 at Vgs=−4 V, Vds = 50 V and a maximum power added efficiency of 51.3% at Vgs=−4 V, Vds = 30 V at 3 GHz on 2 × 50 μmAlGaN/GaN HEMTs on the sapphire substrate, with a gate length of 2 μm and without field-plated gates. To the best of our knowledge, this is the highest level power density reported on the sapphire substrate without field-plate design. The extrinsic cut-off frequency ( ft) and maximumoscillation frequency ( fmax) are 51 GHz and 100 GHz, respectively, on 2 × 50 × 0.15 μm HEMTs. To our knowledge, the sputtered SiNx passivation for AlGaN/GaN HEMTs is a unique technique, which has never beenpublished before.
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| 30. |
- Shiu, Jin-Yu, 1978, et al.
(författare)
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Oxygen Ion Implantation Isolation Planar Process for AlGaN/GaN HEMTs
- 2007
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Ingår i: IEEE Electron Device Letters. ; 28:6, s. 476-478
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Tidskriftsartikel (refereegranskat)abstract
- A multienergy oxygen ion implantation process wasdemonstrated to be compatible with the processing of highpower microwave AlGaN/GaN high electron mobility transistors (HEMTs). HEMTs that are isolated by this process exhibited gate-lag- and drain-lag-free operation. A maximum output power density of 5.3 W/mm at Vgs = −4 V and Vds = 50 V and a maximum power added efficiency of 51.5% at Vgs = −4 V and Vds = 30 V at 3 GHz were demonstrated on HEMTs withoutfield plates on sapphire substrate. This isolation process results in planar HEMTs, circumventing potential problems with enhancedgate leakage due to the gate contacting the 2-D electron gas at themesa sidewall.
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| 31. |
- Suijker, Erwin M., et al.
(författare)
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GaN MMIC power amplifiers for S-band and X- band
- 2008
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Ingår i: 38th European Microwave Conference, EuMC 2008; Amsterdam; Netherlands; 27 October 2008 through 31 October 2008. - 9782874870064 ; , s. 297-300
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Konferensbidrag (refereegranskat)abstract
- The development of two GaN MMIC power amplifiers is reported. The amplifiers are processed in the AlGaN/GaN technology of Chalmers University of Technology using 0.25 ?m HEMTs. The S-band amplifier operates at frequencies from 3 to 4 GHz and has a maximum output power of 5.6 W with an associated efficiency of 28 %. The X-band amplifier has a maximum output power of 4.8 W.
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