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Ohmic contacts to Si-implanted and un-implanted n-type GaN

Published online by Cambridge University Press:  21 February 2011

J. Brown ,
J Ramer ,
K. ZHeng ,
L.F. Lester ,
S.D. Hersee  and
J Zolper
J. Brown
Affiliation:
Center for High Technology Materials, University of New Mexico, Albuquerque, NM 87131
J Ramer
Affiliation:
Center for High Technology Materials, University of New Mexico, Albuquerque, NM 87131
K. ZHeng
Affiliation:
Center for High Technology Materials, University of New Mexico, Albuquerque, NM 87131
L.F. Lester
Affiliation:
Center for High Technology Materials, University of New Mexico, Albuquerque, NM 87131
S.D. Hersee
Affiliation:
Center for High Technology Materials, University of New Mexico, Albuquerque, NM 87131
J Zolper
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87
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Abstract

We report on ohmic contacts to Si-implanted and un-implanted n-type GaN on sapphire. A ring shaped contact design avoids the need to isolate the contact structures by additional implantation or etching. Metal layers of Al and Ti/Al were investigated. On un-implanted GaN, post metalization annealing was performed in an RTA for 30 seconds in N2 at temperatures of 700, 800, and 900°C, A minimum specific contact resistance (rc) of 1.4×10−5 Ω-cm2 was measured for Ti/Al at an annealing temperature of 800°C. Although these values are reasonably low, variations of 95% in specific contact resistance were measured within a 500 µm distance on the wafer. These results are most likely caused by the presence of compensating hydrogen. Specific contact resistance variation was reduced from 95% to 10% by annealing at 900°C prior to metalization. On Si-implanted GaN, un-annealed ohmic contacts were formed with Ti/Al metalization. The implant activation anneal of 1120°C generates nitrogen vacancies that leave the surface heavily n-type, which makes un-annealed ohmic contacts with low contact resistivity possible.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 395: Symposium AAA – Gallium Nitride and Related Materials: The First International Symp , 1995 , 855
Copyright
Copyright © Materials Research Society 1996

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References

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