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Ohmic and Rectifying Contacts to n and p-type GaN Films

Published online by Cambridge University Press:  11 February 2011

H. P. Hall ,
M. A. Awaah ,
A. Kumah ,
K. Das  and
F. Semendy
H. P. Hall
Affiliation:
Tuskegee University, Dept. of Electrical Engineering Tuskegee, AL 36088.
M. A. Awaah
Affiliation:
Tuskegee University, Dept. of Electrical Engineering Tuskegee, AL 36088.
A. Kumah
Affiliation:
Tuskegee University, Dept. of Electrical Engineering Tuskegee, AL 36088.
K. Das
Affiliation:
Tuskegee University, Dept. of Electrical Engineering Tuskegee, AL 36088.
F. Semendy
Affiliation:
Army Research Laboratory Adelphi, MD.
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Abstract

Electrical contacts to both n and p-type GaN films have been investigated using electron-beam evaporated and sputtered films of metals such as Al, Au, Cr, Cu, Ni, Pt, and Ti. Films deposited by electron-beam evaporation for the n-type films with doping levels of 1 × 1018/cm3 and lower showed rectifying characteristics with all the metals studied with the exception of Al. Aluminum contact diodes were ohmic in the as-deposited state. The Pt rectifying contact was near-ideal with an ideality factor close to 1.0. Ideality factors for the other metals were much greater than 1. This deviation from thermionic behavior was interpreted as space charge limited current conduction in the presence of deep-level states. Sputtered films showed very similar characteristics to electron-beam deposited films, with the exception of Ti. The Ti contact was ohmic in the as-deposited state. Non-linear Cu contacts to n-type films became ohmic on annealing. However, for p-type films, Ar ion sputter-cleaning prior to metal deposition by sputtering created ohmic contacts with Cu and Pt. Low resistance ohmic contacts were achieved by ion implantation and anneal of Si in n-type and Mg in p-type films, prior to metallization. The implant parameters and anneal temperatures are currently being optimized.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 743: Symposium L – GaN and Related Alloys , 2002 , L11.58
Copyright
Copyright © Materials Research Society 2003

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References

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