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Effect of Cryogenic Temperature Deposition of Various Metal Contacts to Bulk, Single-Crystal n-type ZnO

Published online by Cambridge University Press:  01 February 2011

Jon Wright ,
L. Stafford ,
B. P. Gila ,
D. P. Norton ,
S. J. Pearton ,
Hung-Ta Wang  and
F. Ren
Jon Wright
Affiliation:
jswright@ufl.edu, University of Florida, Materials Science & Engineering, Materials Science & Engineering, 100 Rhines Hall, Gainesville, FL, 32611, United States
L. Stafford
Affiliation:
jswright@ufl.edu, University of Florida, Materials Science & Engineering, Gainesville, FL, 32611, United States
B. P. Gila
Affiliation:
jswright@ufl.edu, University of Florida, Materials Science & Engineering, Gainesville, FL, 32611, United States
D. P. Norton
Affiliation:
jswright@ufl.edu, University of Florida, Materials Science & Engineering, Gainesville, FL, 32611, United States
S. J. Pearton
Affiliation:
jswright@ufl.edu, University of Florida, Materials Science & Engineering, Gainesville, FL, 32611, United States
Hung-Ta Wang
Affiliation:
jswright@ufl.edu, University of Florida, Chemical Engineering, Gainesville, FL, 32611, United States
F. Ren
Affiliation:
jswright@ufl.edu, University of Florida, Chemical Engineering, Gainesville, FL, 32611, United States
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Abstract

The development of reliable and thermally stable Ohmic and Schottky contacts to ZnO is one of the critical issues related to the fabrication of ZnO-based UV light emitters/detectors and field effect transistors. To date, a number of different metallization schemes and surface cleaning procedures prior to metal deposition have been examined for rectifying contacts on n-ZnO. While these reports have shown that low reactive metals such as Au, Ag and Pd form rectifying contacts with Schottky barrier heights in the 0.6-0.8 eV range, the thermal stability of these contacts is usually extremely poor, with degradation occurring even at 60°C for Au/n-ZnO. One approach to achieving increased barrier heights that has proven successful for GaAs, InP, InGaAs and other compound semiconductors is the use of cryogenic deposition temperatures. In this context, we report in this work on the effect of cryogenic temperature metal deposition on the contact properties of Pd, Pt, Ti, and Ni on single-crystal n-type ZnO. Deposition at both room and low temperature produced contacts with Ohmic characteristics for Ti and Ni metallizations. In comparison, both Pd and Pt contacts showed rectifying characteristics after deposition. All rectifying contacts exhibited barrier heights around 1-2 eV and idealities between 1 and 2. Low temperature deposition gave higher resistances in comparison to room temperature deposition for all cases. Larger contacts also corresponded to an increase in resistance. Changes in contact behavior were measured on Pd to anneal temperatures of ∼300°C, showing an increase in barrier height along with a decrease in ideality with increasing temperature. This difference with annealing temperature is in sharp contrast to previous results for Au contacts to ZnO. There were no differences in near-surface stoichiometry for the different deposition temperatures; however low temperature contacts demonstrated some cracking in Pt and Pd, probably due to surface stress.

Keywords

II-VIZnelectronic material
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 957: Symposium K – Zinc Oxide and Related Materials , 2006 , 0957-K09-02
Copyright
Copyright © Materials Research Society 2007

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