| 1. |
- Sudow, Mattias, 1980, et al.
(author)
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SiC varactors for dynamic load modulation of high power amplifiers
- 2008
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In: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 29:7, s. 728-730
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Journal article (peer-reviewed)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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| 2. |
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| 3. |
- Allerstam, Fredrik, 1978, et al.
(author)
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Comparison between oxidation processes used to obtain the high inversion channel mobility in 4H-SiC MOSFETs
- 2007
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In: Semiconductor Science and Technology. - : IOP Publishing. - 1361-6641 .- 0268-1242. ; 22:4, s. 307-311
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Journal article (peer-reviewed)abstract
- In this work two oxidation methods aimed at improving the silicon face 4H-SiC/SiO 2 interface are compared. One is an oxidation in N 2 O performed in a quartz tube using quartz sample holders and the other is a dry oxidation performed in an alumina tube using alumina sample holders. In n-type metal oxide semiconductor (MOS) capacitors the interface state density near the SiC conduction band edge is estimated using capacitance-voltage (C-V) and thermal dielectric relaxation current (TDRC) measurements. N-channel metal oxide semiconductor field effect transistors (MOSFETs) are characterized by current-voltage (I-V) techniques and the inversion channel mobility is extracted. It is shown that the high inversion channel mobility (154 cm 2 V -1 s -1 ) seen in samples oxidized using alumina correlates with a low interface trap density (3.6 × 10 11 cm -2 ). In the case of N 2 O oxidation the mobility is lower (24 cm 2 V -1 s -1 ) and the interface trap density is higher (1.6 × 10 12 cm -2 ). Room temperature C-V measurements are of limited use when studying traps near the conduction band edge in MOS structures while the TDRC measurement technique gives a better estimate of their density. © 2007 IOP Publishing Ltd.
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| 4. |
- Allerstam, Fredrik, 1978, et al.
(author)
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Formation of deep traps at the 4H-SiC/SiO2 interface when utilizing sodium enhanced oxidation
- 2007
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In: Materials Science Forum. - 1662-9752 .- 0255-5476. ; 556-557, s. 517-520
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Conference paper (peer-reviewed)abstract
- This paper reports studies of deep acceptor-type interface traps at the 4H-SiC/SiO2 interface. These traps are created during sodium enhanced oxidation of Si-terminated 4H-SiC. The trap concentration is above 3×1012 cm-2 and their activation energy is larger than 0.8 eV.
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| 7. |
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| 8. |
- Fager, Christian, 1974, et al.
(author)
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High Efficiency Transmitter Using Varactor Based Dynamic Load Modulation
- 2010
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In: IEEE International Microwave Workshop Series on “RF Front-ends for Software Defined and Cognitive Radio Solutions”. - 9781424457526 ; , s. 37-40
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Conference paper (peer-reviewed)abstract
- This paper presents results for a dynamic loadmodulation transmitter where an existing 1 GHz LDMOSpower amplifier is combined with a varactor based tuneableload network to produce a dramatic efficiency improvementfor modulated signals. The transmitter is combinedwith a dedicated linearization method to achieve anaverage PAE of 53% for a WCDMA signal at 7 dB PAPR.The results demonstrate the potential of dynamic loadmodulation for future transmitters combining flexibilityand high efficiency at a low cost.
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| 9. |
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| 10. |
- Gudjonsson, Gudjon, 1973, et al.
(author)
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Design and Fabrication of 4H-SiC RF MOSFETs
- 2007
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In: IEEE Transactions on Electron Devices. - 1557-9646 .- 0018-9383. ; 54:12, s. 3138-3145
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Journal article (peer-reviewed)abstract
- We present simulations, fabrication and analysis of 4H-SiC RF power MOSFETs. We obtain an extrinsic transition frequency of 11.2 GHz and an f max = 11.9 GHz, a breakdown voltage above 200 V and an output power of 1.9 W/mm at 3 GHz. The measured devices are double fingered, source-gate-draingate-source with 2 × 0.4 mm total gate width and the nominal channel length of the devices is 0.5 μm. To the authors knowledge, this is the highest transition frequency and output power density ever reported for SiC RF MOSFETs. The antipunchthrough is introduced as a way to take advantage of the SiC's material properties. A detailed description of the device processing is also given. © 2007 IEEE.
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