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Ohmic and Highly Reflective Ag based contacts on p-GaN for Resonant Cavity Light Emitting Diodes

Published online by Cambridge University Press:  02 March 2011

V. Kumbham
Affiliation:
Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown ,WV 26506
S. Kuchibhatla
Affiliation:
Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown ,WV 26506
K. Lee
Affiliation:
Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown ,WV 26506
L.E. Rodak
Affiliation:
Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown ,WV 26506
V. Narang
Affiliation:
Department of Physics, West Virginia University, Morgantown, WV 26506, USA
D. Korakakis
Affiliation:
Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown ,WV 26506
L.A. Hornak
Affiliation:
Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown ,WV 26506
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Abstract

Low resistance and high reflectance ohmic contacts on p-type GaN were achieved using an Ag-based metallization scheme. The ohmic nature of the contacts can be obtained by annealing the contacts in an O2 ambient. However, Ag based contacts degrade due to agglomeration of Ag when annealed above 400 oC [1]. In this work a Ni (1 nm)/Ag (150 nm)/Pt (50 nm)/Ni (20 nm)/Au (50 nm) metallization stack is investigated to reduce Ag agglomeration. The inclusion of platinum as a diffusion barrier is expected to suppress excess oxygen diffusion into the Ag films thereby preventing Ag agglomeration and can also provide high thermal stability when compared to other metallization schemes. The reflectivity of this kind of metallization scheme is around 85-90 % in the wavelength range of 400-600 nm making it suitable for blue and green LEDs, with a specific contact resistivity value comparable to other well developed contacts to p-GaN.

Type
Research Article
Copyright
Copyright © Materials Research Society 2011

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References

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