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Reduction of Base Access Resistance in AlGaN/GaN Heterojunction Bipolar Transistors using GaInN Base Cap Layer and Selective Epitaxial Growth

Published online by Cambridge University Press:  01 February 2011

Jay M Shah ,
Thomas Gessmann ,
Hong Luo ,
Yangang Xi ,
Kaixuan Chen ,
Jong Kyu Kim  and
E. Fred Schubert
Jay M Shah
Affiliation:
shahjm@rpi.edu, Rensselaer Polytechnic Institute, ECSE, 110 8th Street, CII Bldg, Room 7307, Troy, NY, 12180, United States
Thomas Gessmann
Affiliation:
gessmann@rpi.edu, Rensselaer Polytechnic Institute, Electrical, Computer, and Systems Engineering, United States
Hong Luo
Affiliation:
luoh@rpi.edu, Rensselaer Polytechnic Institute, Department of Physics, Applied Physics, and Astronomy, United States
Yangang Xi
Affiliation:
xiy@rpi.edu, Rensselaer Polytechnic Institute, Department of Physics, Applied Physics, and Astronomy, United States
Kaixuan Chen
Affiliation:
chenk4@rpi.edu, Rensselaer Polytechnic Institute, Department of Physics, Applied Physics, and Astronomy, United States
Jong Kyu Kim
Affiliation:
kimj4@rpi.edu, Rensselaer Polytechnic Institute, Electrical, Computer, and Systems Engineering, United States
E. Fred Schubert
Affiliation:
EFSchubert@rpi.edu, Rensselaer Polytechnic Institute, Electrical, Computer, and Systems Engineering, United States
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Abstract

One of the major challenges affecting the performance of Npn AlGaN/GaN heterojunction bipolar transistors (HBTs) is the high base access resistance, which is comprised of the base contact resistance and the base bulk resistance. A novel concept is proposed to reduce the base access resistance in Npn AlGaN/GaN HBTs by employing polarization-enhanced contacts and selective epitaxial growth of the base and emitter. In addition, this technique reduces the exposed base surface area, which results in a lower surface recombination current. Such a structure would enable better performance of AlGaN/GaN HBTs in terms of higher current gain and a lower offset voltage. Theoretical calculations on polarization-enhanced contacts predict p-type specific contact resistance lower than 10-5 Ωcm2. Experimental results using transmission line measurement (TLM) technique yield specific contact resistances of 5.6×10-4 Ωcm2 for polarization-enhanced p-type contacts and 7.8×10-2 Ωcm2 for conventional p-type contacts.

Keywords

nitrideepitaxyIII-V
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 892 , 2005 , 0892-FF13-10
Copyright
Copyright © Materials Research Society 2006

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References

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