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Formation of Ni/Pt/Au Ohmic Contacts to p-GaN

Published online by Cambridge University Press:  10 February 2011

Ja-Soon Jang ,
Hyo-Gun Kim ,
Kyung-Hyun Park ,
Chang-Sub Um ,
Il-Ki Han ,
Sun-Ho Kim ,
Heong-Kyu Jang  and
Seong-Ju Park
Ja-Soon Jang
Affiliation:
Deptartment of Materials Science and Engineering, Kwangju Institute of Science and Technology, Kwangju 506-712, Korea
Hyo-Gun Kim
Affiliation:
Deptartment of Materials Science and Engineering, Kwangju Institute of Science and Technology, Kwangju 506-712, Korea
Kyung-Hyun Park
Affiliation:
Photonics Research Center, Korea Institute of Science and Technology, P.O. Box 130, Cheongyang, Seoul, Korea
Chang-Sub Um
Affiliation:
Photonics Research Center, Korea Institute of Science and Technology, P.O. Box 130, Cheongyang, Seoul, Korea
Il-Ki Han
Affiliation:
Photonics Research Center, Korea Institute of Science and Technology, P.O. Box 130, Cheongyang, Seoul, Korea
Sun-Ho Kim
Affiliation:
Photonics Research Center, Korea Institute of Science and Technology, P.O. Box 130, Cheongyang, Seoul, Korea
Heong-Kyu Jang
Affiliation:
Kumho Information and Telecommunication Laboratory, Kwangju 506-712, Korea
Seong-Ju Park
Affiliation:
Deptartment of Materials Science and Engineering, Kwangju Institute of Science and Technology, Kwangju 506-712, Korea
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Abstract

We report a new Ni/Pt/Au (20/30/80 nm) metallization scheme to achieve a low ohmic contacts to p-type GaN with a carrier concentration of 9.4 × 1016 cm-3. A Mg-doped GaN layer (0.5 μm) was grown on (0001) sapphire substrate by metalorganic chemical vapor deposition (MOCVD). All metal thin films were deposited on the p-GaN layer in an electron-beam evaporation system. Samples were annealed by a rapid thermal annealing (RTA) process at a range of temperatures from 300 °C to 850 °C under a flowing Ar atmosphere. A circulartransmission line model (c-TLM) was employed to calculate the specific contact resistance, and current-voltage (I-V) data were measured with HP4155A. The Ni/Pt/Au contacts without the annealing process showed nearly rectifying characteristics. The ohmic contacts were formed on the samples annealed at 500 °C for 30 sec and the I-V data showed a linear behavior. The specific contact resistance was 2.1 × 10-2 Ωcm2. However with increasing the annealing temperature above 600 °C, ohmic contacts were again degraded. Auger electron spectroscopy (AES) depth profiles were used to investigate the interfacial reactions between the trilayer and GaN. AES results suggested that Pt plays a significant role in forming ohmic contact as an acceptor at the interface. Atomic force microscope (AFM) also showed that the samples with good ohmic contact have very smooth surface.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 482 , 1997 , 1053
Copyright
Copyright © Materials Research Society 1998

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