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Low Resistance Ohmic Contact on p-type GaN Grown by Plasma-Assisted Molecular Beam Epitaxy

Published online by Cambridge University Press:  15 February 2011

Myung C. Yoo ,
J. W. Lee ,
J. M. Myoung ,
K. H. Shim  and
K. Kim
Myung C. Yoo
Affiliation:
Photonics Semiconductor Laboratory, Samsung Advanced Institute of Technology, P.O. Box 111, Suwon 440-600, Korea
J. W. Lee
Affiliation:
Photonics Semiconductor Laboratory, Samsung Advanced Institute of Technology, P.O. Box 111, Suwon 440-600, Korea
J. M. Myoung
Affiliation:
Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA
K. H. Shim
Affiliation:
Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA
K. Kim
Affiliation:
Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA
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Abstract

Ohmic contacts on p-type GaN have been investigated. High quality GaN epilayers on cplane sapphire were prepared using plasma-assisted molecular beam epitaxy that utilized an inductively coupled rf nitrogen plasma source and solid source beams. The resulting film thickness and the doping concentration of the grown samples were in the range of 0.7–1.35 μm and 1018 – 1020/cm3, respectively. The metallization consisted of high work function metal bilayers which included a combinations of 25 nm-thick Ni, Ti, Pt and/or Cr and 200 nm-thick Au on the highly p-doped GaN in a transmission line model pattern. Ohmic contacts were formed by alloying the bi-layers using rapid thermal annealing (RTA) at temperatures in the range of 300–700 °C for 1 min under nitrogen ambient. Current-voltage measurements showed that the specific contact resistance was as low as 1.2 × 10 −4 Ω–cm2 for the sample having 1.4 × 1020/cm3p-type doping concentration with a Cr/Au contact annealed at 500 °C for 1 min by RTA. Judging from the scanning Auger microscopy results and the glancing angle x-ray diffraction analysis, this resistance is attributed to Cr diffusion into the GaN layer.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 423: Symposium E – III-Nitride, SiC, and Diamond Materials for Electronic , 1996 , 131
Copyright
Copyright © Materials Research Society 1996

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