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Metal-Semiconductor Contacts and CPW MMIC Issues for AlGaN/GaN FETs

Published online by Cambridge University Press:  17 March 2011

Bart Jacobs ,
Mark Kramer ,
Bram van Straaten ,
Thieu Kwaspen ,
Fouad Karouta ,
Peter de Hek ,
Raymond van Dijk  and
Frank van Vliet
Bart Jacobs
Affiliation:
Eindhoven University of Technology, Department of Electrical Engineering, Opto-Electronic Devices group, P.O. Box 513, NL-5600 MB, Eindhoven, The, Netherlands
Mark Kramer
Affiliation:
Eindhoven University of Technology, Department of Electrical Engineering, Opto-Electronic Devices group, P.O. Box 513, NL-5600 MB, Eindhoven, The, Netherlands
Bram van Straaten
Affiliation:
Eindhoven University of Technology, Department of Electrical Engineering, Opto-Electronic Devices group, P.O. Box 513, NL-5600 MB, Eindhoven, The, Netherlands
Thieu Kwaspen
Affiliation:
Eindhoven University of Technology, Department of Electrical Engineering, Opto-Electronic Devices group, P.O. Box 513, NL-5600 MB, Eindhoven, The, Netherlands
Fouad Karouta
Affiliation:
Eindhoven University of Technology, Department of Electrical Engineering, Opto-Electronic Devices group, P.O. Box 513, NL-5600 MB, Eindhoven, The, Netherlands
Peter de Hek
Affiliation:
TNO-FEL laboratories, The Hague, The, Netherlands
Raymond van Dijk
Affiliation:
TNO-FEL laboratories, The Hague, The, Netherlands
Frank van Vliet
Affiliation:
TNO-FEL laboratories, The Hague, The, Netherlands
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Abstract

In this report two different aspects in the development of AlGaN/GaN power amplifiers will be discussed. In the first part of this paper we report on the optimization of the Ti/Al/Ni/Au metallization scheme on a doped AlGaN/GaN FET structure. By a systematic investigation we were able to reduce the contact resistance to 0.2 ωmm (7.3×10×7ωcm2). The Al/Ti thickness ratio for this contact was 6, which according to the Al-Ti binary phase diagram, does not result in excess Ti which should react with nitrogen in the AlGaN layer to render the surface heavily doped. Preliminary results on Schottky contacts indicate an improvement in the reverse leakage current if a RIE oxygen plasma in combination with a NH4OH dip is performed prior to metallization.

Coplanar waveguides on AlN are discussed in the second part of this paper. These transmission lines can be used in AlGaN/GaN power amplifiers if no via-hole technology is available or if a hybrid solution is pursued. The signal line should have a large metal cross- sectional area (> 5 × 50 [.proportional]m2) in order to carry enough current in the output stage of an amplifier. It is shown that CPWs with large dimensions show non-quasi TEM behavior related to propagation of parallel plate modes.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 639: Symposium G – GaN and Related Alloys-2000 , 2000 , G13.9
Copyright
Copyright © Materials Research Society 2001

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References

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