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Evaluation of SiC MESFET structures using large-signal time-domain simulations
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
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2002 (English)In: Materials Science Forum Vols. 389-393, 2002, Vol. 389-3, 1395-1398 p.Conference paper (Refereed)
Abstract [en]

When designing transistors for microwave power applications a good understanding of their large signal behaviour in a real circuit context is essential. We have used the device simulator Medici in a novel way to simulate the large signal high frequency time domain properties of different SiC MESFET structures. The simulations show that even for transistors with good DC properties the exact design of the channel-buffer and the buffer-substrate regions is important when a good high power RF performance is required. Our simulations indicate that output power densities above 6W/mm are possible if heating problems are solved.

Place, publisher, year, edition, pages
2002. Vol. 389-3, 1395-1398 p.
Keyword [en]
large-signal, MESFETs, microwave, power, simulation, time-domain
National Category
Natural Sciences
URN: urn:nbn:se:liu:diva-48829OAI: diva2:269725
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2010-02-25
In thesis
1. Silicon Carbide Microwave Transistors and Amplifiers
Open this publication in new window or tab >>Silicon Carbide Microwave Transistors and Amplifiers
2005 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Ibis work deals with silicon carbide (SiC) metal semieonduetor field effect transistors (MESFETs) and microwave amplifiers using them. The wide bandgap (WBG) semiconductors silicon carbide and gallium nitride have a large potential for microwave power generation. The high power density combined with the comparably high impedance attainable by devices in these materials also offers new possibilities for wideband high power microwave systems. To realise these possibilities we need transistors that are well understood and optimised and amplifier designs that take advantage of the broadband possibilities offered by the transistors.

We have developed and used physical drift-diffusion simulation models for SiC MESFETs. The simulation results showed a large influence of the doping and thickness of the channel and buffer layers, and the properties of the semi-insulating substrate on the DC and small signal device performance. A comparison between the physical simulations and measured device characteristics has also been carried out. A novel and efficient way to extend the physical simulations to the large signal high frequency domain has been developed. The method was used to investigate experimentally detected problems in the dynamies of the transistors during large signal operation and to further optimise the device structure.

In this work a number of broadband SiC MESFET amplifiers were designed, fabricated and characterized. The packaging and charaeterisation of transistors is described and the design and characterisation of the amplifiers are presented.

A 100-500 MHz amplifier showed a measured output power above 20 W and gain >15 dB across the band and a peak power of 26 W at 400 MHz, corresponding to a power density of 5.2 W/mm, with an associated power added efficiency (PAE) of 46 %. A 0.8-2 GHz feedback amplifier showed a measured output power above 5 W, gain >7 dB and PAE above 15 % across the band. A two stage 2.8-3.3 GHz amplifier had a maximum measured output power of 12.6 W with 22 dB gain and 9% PAE measured at 2.8 GHz. These results clearly show that SiC devices have a large potential for microwave power amplifiers in general and broadband amplifiers in particular.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2005. 44 p.
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1186
SiC, MESFET, Physical simulations, Microwave power amplifier
National Category
Natural Sciences
urn:nbn:se:liu:diva-31212 (URN)LiU-TEK-LIC-2005:41 (Local ID)91-85457-03-5 (ISBN)LiU-TEK-LIC-2005:41 (Archive number)LiU-TEK-LIC-2005:41 (OAI)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2010-02-25Bibliographically approved

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Wahab, Qamar
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Semiconductor MaterialsThe Institute of Technology
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