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- Andersson, Kristoffer, 1976, et al.
(author)
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Resistive SiC-MESFET mixer
- 2002
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In: IEEE Microwave and Wireless Components Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1531-1309 .- 1558-1764. ; 12:4, s. 119-121
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Journal article (peer-reviewed)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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- Bengtsson-Palme, Johan, 1985, et al.
(author)
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Metaxa2: Improved identification and taxonomic classification of small and large subunit rRNA in metagenomic data
- 2015
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In: Molecular Ecology Resources. - : Wiley. - 1755-098X .- 1755-0998. ; 15:6, s. 1403-1414
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Journal article (peer-reviewed)abstract
- The ribosomal rRNA genes are widely used as genetic markers for taxonomic identification of microbes. Particularly the small subunit (SSU; 16S/18S) rRNA gene is frequently used for species- or genus-level identification, but also the large subunit (LSU; 23S/28S) rRNA gene is employed in taxonomic assignment. The metaxa software tool is a popular utility for extracting partial rRNA sequences from large sequencing data sets and assigning them to an archaeal, bacterial, nuclear eukaryote, mitochondrial or chloroplast origin. This study describes a comprehensive update to metaxa – metaxa2 – that extends the capabilities of the tool, introducing support for the LSU rRNA gene, a greatly improved classifier allowing classification down to genus or species level, as well as enhanced support for short-read (100 bp) and paired-end sequences, among other changes. The performance of metaxa2 was compared to other commonly used taxonomic classifiers, showing that metaxa2 often outperforms previous methods in terms of making correct predictions while maintaining a low misclassification rate. metaxa2 is freely available from http://microbiology.se/software/metaxa2/
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- Dynefors, Kristina, 1977, et al.
(author)
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research and development of SiC Static Induction transistor
- 2003
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In: GHz2003 conference, Linköping 2003.
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Conference paper (other academic/artistic)abstract
- A fabrication process for SiC Static Induction Transistors (SITs) is developed and tested. Simulated and measured results of the device are presented. The complete fabrication process involves only 5 lithography steps, due to the self-aligned process used for mesa, ohmic contacts and gates. This makes the process fast and minimize the risk of process errors. Only optical lithography is used in the process, why dimensions are not optimised. Mesa widths of 2, 3, 4 and 5 µm are processed. Since the process is scalable, better performance can be expected with smaller widths achieved by the use electron beam lithography. Preliminary results indicate FET operation with a maximum current density of 110 mA/mm.
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- Eriksson, Joakim, 1969
(author)
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Silicon Carbide Microwave Devices
- 2002
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Doctoral thesis (other academic/artistic)abstract
- This work deals with silicon carbide (SiC) microwave devices. It treats two devices; the Schottky diode and the metal semiconductor field effect transistor (MESFET). Different MESFET materials, fabrication processes, theoretical models for physical simulation, and device models are presented. The aim of this work is to improve the understanding of these devices and their performance by careful design. An optimisation design technique for the SiC microwave Schottky diode is developed. Depending of the desired punch-through voltage a certain calculated drift layer thickness and doping concentration for the Schottky diode provides an optimum when designing for cut-off frequency. Schottky diodes that behave according to the models presented are demonstrated. For a 5 µm anode radius diode a cut-off frequency (fcut) of 91 GHz was calculated . To our knowledge this is the highest fcut presented for a SiC Schottky diode. A singly balanced diode mixer was measured. The input third order intermodulation intercept point is 31dBm. The mixer has a conversion loss of 5.0 dB at 850 MHz RF. Eleven MESFET structures have been investigated both by physical drift-diffusion (DD) simulations, and measurements. The models used in the DD simulations are described in detail, and approximations of published data have been presented. In particular different buffer structures, and their influence on device performance have been investigated. Measurements on 11 different MESFET materials are presented. In the research performed at Chalmers, devices with very good DC characteristics have been manufactured. The best RF device has a saturated drain current of 270 mA/mm, a maximum transconductance of 35 mS/mm, a breakdown voltage of >100 V, and a pinch-off voltage of -15 V. The high frequency performance of this device are an fmax of 27 GHz, an fT,ext of 8 GHz, and an output power density of 3.2 W/mm with an associated gain of 14 dB at 3 GHz. A resistive FET mixer using a 3.2 mm gate periphery MESFET is presented, and it had a conversion loss of 10 dB, and a IIP3 of 36 dBm at 3.3 GHz.A small signal model for the MESFET in coldFET operation is given.
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