Abstract
We investigated the effect of a 20-nm-thick Cu capping layer on the electrical and the optical properties of Ag contacts (200 nm thick) in order to form thermally stable and low-resistance p-type ohmic reflectors for high-performance vertical light-emitting diodes (LEDs). The Ag/Cu contacts give a specific contact resistance of 6.7 × 10−4 Ωcm2 and a reflectance of ∼78% at a wavelength of 460 nm when annealed at 400 °C for 1 min in air, which are better than that of Ag only contacts. Blue LEDs fabricated with the Ag/Cu contacts give a forward voltage of 2.90 V at an injection current of 20mA, which is lower than that (2.97 V) of LEDs with Ag only contacts. The LEDs with the 400 °C-annealed Ag/Cu contacts exhibit ∼27% higher output power (at 20 mA) than LEDs with the 400 °C-annealed Ag only contacts. X-ray photoemission spectroscopy examinations were carried out to describe the improved electrical behaviour of the Ag/Cu contacts.
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References
S. Nakamura, T. Mukai and M. Senoh, Appl. Phys. Lett. 64, 1687 (1994).
D. A. Steigerwald, J. C. Bhat, D. Collins, R. M. Fletcher and M. O. Holcomb, IEEE J. Sel. Top. Quantum Electron. 8, 310 (2002).
J. J. Wierer, D. A. Steigerwald, M. R. Krames, J. J. Shea and M. J. Ludowise, Appl. Phys. Lett. 78, 3379 (2001).
J-O. Song, D-S. Leem, J-S. Kwak, O-H. Nam, Y. Park and T-Y. Seong, IEEE Photonics Technol. Lett. 16, 1450 (2004).
G. Elger, M. Hutter, H. Oppermann, R. Aschenbrenner, H. Reich and E. Jager, Microsyst. Technol. 7, 239 (2002).
D. L. Hibbard, S. P. Jung, C. Wang, D. Ullery, Y. S. Zhao and H.-P. Lee, Appl. Phys. Lett. 83, 311 (2003).
S. Y. Kim and J-L. Lee, Electrochem. Solid-State Lett. 7, G210 (2004).
J-O. Song, J-S. Kwak and T-Y. Seong, Appl. Phys. Lett. 86, 062103 (2005).
J-O. Song, D-S. Leem, J. S. Kwak, O. H. Nam, Y. Park and T-Y. Seong, Appl. Phys. Lett. 83, 4990 (2003).
S-H. Park, J-W. Jeon, J-T. Oh and T-Y. Seong, J. Korean Phys. Soc. 59, 156 (2011).
S. Jung, Y-H. Kim, J-H. Oh and T-Y. Seong, Superlattices Microstruct. 46, 578 (2009).
I-C. Chen, Y.-D. Chen, C.-C. Hsieh, C.-H. Kuo and L.-C. Chang, J. Electrochem. Soc. 158, H285 (2011).
J-S. Jang and T-Y. Seong, J. Vac. Sci. Technol., B 17, 2667 (1999).
H. W. Jang and J.-L. Lee, Appl. Phys. Lett. 85, 5920 (2004).
K. M. Tracy, P. J. Hartlieb, S. Einfeldt, R. F. Davis, E. H. Hurt and R. J. Nemanich, J. Appl. Phys. 94, 3939 (2003).
J-O. Song, J. S. Kwak, Y. Park and T-Y. Seong, Appl. Phys. Lett. 86, 062104 (2005).
J. Sun, K. A. Rickert, J. M. Redwing, A. B. Ellis, F. J. Himpsel and T. F. Kuech, Appl. Phys. Lett. 76, 415 (2000).
V. M. Bermudez, D. D. Koleske and A. E. Wickenden, Appl. Surf. Sci. 126, 69 (1998).
J. H. Son, G. H. Jung and J-L. Lee, Appl. Phys. Lett. 93, 012102 (2008).
J-P. Crocombette, H. Monestrol and F. Willaime, Phys. Rev. B 66, 024114 (2002).
Y. H. Song, J. H. Son, G. H. Jung and J-L. Lee, Electrochem. Solid-State Lett. 13, H173 (2010)
G. H. Jung, J. H. Son, Y. H. Song and J-L. Lee, Appl. Phys. Lett. 96, 201904 (2010).
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Joo, MK., Jung, SY. & Seong, TY. Improving the thermal stability of Ag Ohmic contacts for GaN-based vertical light-emitting diodes with a Cu capping layer. Journal of the Korean Physical Society 60, 857–861 (2012). https://doi.org/10.3938/jkps.60.857
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DOI: https://doi.org/10.3938/jkps.60.857