Abstract

The formation of thermally stable and low resistance Ti/Al-based ohmic contacts to N-polar n-GaN for high-power vertical light-emitting diodes (VLEDs) using a Ta diffusion barrier is presented. Before annealing, both Ti/Al/Au and Ti/Ta/Al/Au contacts reveal ohmic behavior with specific contact resistances of 2.4 × 10−4 and 1.2 × 10−4 Ωcm2, respectively. However, unlike the Ti/Al/Au samples that are electrically degraded with increasing annealing time at 250 °C, the Ti/Ta/Al/Au samples remain thermally stable even after annealing for 600 min. LEDs fabricated with the Ti/Ta/Al/Au contacts yield 8.3% higher output power (at 300 mA) than LEDs with the Ti/Al/Au contact. X-ray photoemission spectroscopy results show that the Ta layer serves as an efficient barrier to the indiffusion of oxygen toward the GaN. On the basis of the XPS and electrical results, the annealing dependence of the electrical characteristics of Ti/Al-based contacts are described and discussed.

© 2014 Optical Society of America

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  1. W. S. Wong, T. Sands, N. W. Cheung, M. Kneissl, D. P. Bour, P. Mei, L. T. Romano, and N. M. Johnson, “Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off,” Appl. Phys. Lett. 75(10), 1360–1362 (1999).
    [CrossRef]
  2. S. Y. Lee, K. K. Choi, H.-H. Jeong, H. S. Choi, T.-H. Oh, J.-O. Song, and T.-Y. Seong, “Wafer-level fabrication of GaN-based vertical light-emitting diodes using a multi-functional bonding material system,” Semicond. Sci. Technol. 24(9), 092001 (2009).
    [CrossRef]
  3. C. F. Chu, C. C. Yu, H. C. Cheng, C. F. Lin, and S. C. Wang, “Comparison of p-side down and p-side up GaN light-emitting diodes fabricated by laser lift-off,” Jpn. J Appl. Phys. Part 2 Lett 42, 147–149 (2003).
  4. J. S. Ha, S. W. Lee, H. J. Lee, H.-J. Lee, S. H. Lee, H. Goto, T. Kato, K. Fujii, M. W. Cho, and T. Yao, “The fabrication of vertical LEDs using chemical lift-off process,” IEEE Photon. Technol. Lett. 20(3), 175–177 (2008).
    [CrossRef]
  5. V. Ramachandran, R. M. Feenstra, W. L. Sarney, L. Salamanca-Riba, and D. W. Greve, “Optimized structural properties of wurtzite GaN on SiC (0001) grown by molecular beam epitaxy,” J. Vac. Sci. Technol. A 18(4), 1915–1918 (2000).
    [CrossRef]
  6. M. H. Kim, Y. C. Bang, N. M. Park, C. J. Choi, T.-Y. Seong, and S.-J. Park, “Growth of high-quality GaN on Si (111) substrate by UVCVD,” Appl. Phys. Lett. 78, 2858 (2001).
    [CrossRef]
  7. J.-O. Song, J.-S. Ha, and T.-Y. Seong, “Ohmic contact technology for GaN-based LEDs: role of p-type Contact,” IEEE Trans. Electron. Dev. 57(1), 42–59 (2010).
    [CrossRef]
  8. B. P. Luther, S. E. Mohney, T. N. Jackson, M. Asif Khan, Q. Chen, and J. W. Yang, “Investigation of the mechanism for Ohmic contact formation in Al and Ti/Al contacts to n -type GaN,” Appl. Phys. Lett. 70(1), 57–59 (1997).
    [CrossRef]
  9. M. E. Lin, Z. Ma, F. Y. Huang, Z. F. Fan, L. H. Allen, and H. Morkoç, “Low resistance ohmic contacts on wide band‐gap GaN,” Appl. Phys. Lett. 64(8), 1003 (1994).
    [CrossRef]
  10. L. F. Lester, J. M. Brown, J. C. Ramer, L. Zhang, S. D. Hersee, and J. C. Zolper, “Nonalloyed Ti/Al ohmic contacts to n‐type GaN using high‐temperature premetallization anneal,” Appl. Phys. Lett. 69(18), 2737–2739 (1996).
    [CrossRef]
  11. U. Karrer, O. Ambacher, and M. Stutzmann, “Influence of crystal polarity on the properties of Pt/GaN Schottky diodes,” Appl. Phys. Lett. 77(13), 2012–2014 (2000).
    [CrossRef]
  12. J. S. Kwak, K. Y. Lee, J. Y. Han, J. Cho, S. Chae, O. H. Nam, and Y. Park, “Crystal-polarity dependence of Ti/Al contacts to freestanding n-GaN substrate,” Appl. Phys. Lett. 79(20), 3254–3256 (2001).
    [CrossRef]
  13. H. W. Jang, J.-H. Lee, and J.-L. Lee, “Characterization of band bending on Ga-face and N-face GaN films grown by metalorganic chemical-vapor deposition,” Appl. Phys. Lett. 80(21), 3955–3957 (2002).
    [CrossRef]
  14. H. Kim, J.-H. Ryou, R. D. Dupuis, S.-N. Lee, Y. Park, J.-W. Jeon, and T.-Y. Seong, “Electrical characteristics of contacts to thin film N-polar n-type GaN,” Appl. Phys. Lett. 93(19), 192106 (2008).
    [CrossRef]
  15. T. Jang, S. N. Lee, O. H. Nam, and Y. Park, “Investigation of Pd/Ti/Al and Ti/Al ohmic contact materials on Ga-face and N-face surfaces of n-type GaN,” Appl. Phys. Lett. 88(19), 193505 (2006).
    [CrossRef]
  16. J.-W. Jeon, T.-Y. Seong, H. Kim, and K.-K. Kim, “TiN/Al ohmic contacts to N-face n-type GaN for high-performance vertical light-emitting diodes,” Appl. Phys. Lett. 94(4), 042102 (2009).
    [CrossRef]
  17. J.-W. Jeon, S.-H. Park, S.-Y. Jung, S. Y. Lee, J. Moon, J.-O. Song, and T.-Y. Seong, “Formation of low-resistance ohmic contacts to N-face n-GaN for high-power GaN-based vertical light-emitting diodes,” Appl. Phys. Lett. 97(9), 092103 (2010).
    [CrossRef]
  18. J.-W. Jeon, S. Y. Lee, J.-O. Song, and T.-Y. Seong, “Highly reliable ohmic contacts to N-polar n-type GaN for vertical light-emitting diodes via laser-annealing,” IEEE Photon. Technol. Lett. 23, 1784–1786 (2011).
    [CrossRef]
  19. P. Boguslawski, E. L. Briggs, and J. Bernholc, “Native defects in gallium nitride,” Phys. Rev. B. 51(23), 17255–17258 (1995).
    [CrossRef] [PubMed]
  20. H. Kim, S.-N. Lee, Y. Park, J. S. Kwak, and T.-Y. Seong, “Metallization contacts to nonpolar a-plane n-type GaN,” Appl. Phys. Lett. 93(3), 032105 (2008).
    [CrossRef]
  21. J.-O. Song, D.-S. Leem, and T.-Y. Seong, “Formation of low resistance and transparent ohmic contacts to p-type GaN using Ni–Mg solid solution,” Appl. Phys. Lett. 83(17), 3513–3515 (2003).
    [CrossRef]
  22. H. W. Jang, S. Y. Kim, and J.-L. Lee, “Mechanism for ohmic contact formation of oxidized Ni/Au on p-type GaN,” J. Appl. Phys. 94(3), 1748–1750 (2003).
    [CrossRef]
  23. J. K. Kim, J. L. Lee, J. W. Lee, H. E. Shin, Y. J. Park, and T. I. Kim, “Low resistance Pd/Au ohmic contacts to p-type GaN using surface treatment,” Appl. Phys. Lett. 73(20), 2953–2955 (1998).
    [CrossRef]
  24. I. Waki, H. Fujioka, K. Ono, M. Oshima, H. Miki, and A. Fukizawa, “The effect of surface cleaning by wet Treatments and ultra high vacuum annealing for ohmic contact formation of P-type GaN,” Jpn. J. Appl. Phys. 39(Part 1, No. 7B), 4451–4455 (2000).
    [CrossRef]

2011

J.-W. Jeon, S. Y. Lee, J.-O. Song, and T.-Y. Seong, “Highly reliable ohmic contacts to N-polar n-type GaN for vertical light-emitting diodes via laser-annealing,” IEEE Photon. Technol. Lett. 23, 1784–1786 (2011).
[CrossRef]

2010

J.-O. Song, J.-S. Ha, and T.-Y. Seong, “Ohmic contact technology for GaN-based LEDs: role of p-type Contact,” IEEE Trans. Electron. Dev. 57(1), 42–59 (2010).
[CrossRef]

J.-W. Jeon, S.-H. Park, S.-Y. Jung, S. Y. Lee, J. Moon, J.-O. Song, and T.-Y. Seong, “Formation of low-resistance ohmic contacts to N-face n-GaN for high-power GaN-based vertical light-emitting diodes,” Appl. Phys. Lett. 97(9), 092103 (2010).
[CrossRef]

2009

J.-W. Jeon, T.-Y. Seong, H. Kim, and K.-K. Kim, “TiN/Al ohmic contacts to N-face n-type GaN for high-performance vertical light-emitting diodes,” Appl. Phys. Lett. 94(4), 042102 (2009).
[CrossRef]

S. Y. Lee, K. K. Choi, H.-H. Jeong, H. S. Choi, T.-H. Oh, J.-O. Song, and T.-Y. Seong, “Wafer-level fabrication of GaN-based vertical light-emitting diodes using a multi-functional bonding material system,” Semicond. Sci. Technol. 24(9), 092001 (2009).
[CrossRef]

2008

J. S. Ha, S. W. Lee, H. J. Lee, H.-J. Lee, S. H. Lee, H. Goto, T. Kato, K. Fujii, M. W. Cho, and T. Yao, “The fabrication of vertical LEDs using chemical lift-off process,” IEEE Photon. Technol. Lett. 20(3), 175–177 (2008).
[CrossRef]

H. Kim, J.-H. Ryou, R. D. Dupuis, S.-N. Lee, Y. Park, J.-W. Jeon, and T.-Y. Seong, “Electrical characteristics of contacts to thin film N-polar n-type GaN,” Appl. Phys. Lett. 93(19), 192106 (2008).
[CrossRef]

H. Kim, S.-N. Lee, Y. Park, J. S. Kwak, and T.-Y. Seong, “Metallization contacts to nonpolar a-plane n-type GaN,” Appl. Phys. Lett. 93(3), 032105 (2008).
[CrossRef]

2006

T. Jang, S. N. Lee, O. H. Nam, and Y. Park, “Investigation of Pd/Ti/Al and Ti/Al ohmic contact materials on Ga-face and N-face surfaces of n-type GaN,” Appl. Phys. Lett. 88(19), 193505 (2006).
[CrossRef]

2003

C. F. Chu, C. C. Yu, H. C. Cheng, C. F. Lin, and S. C. Wang, “Comparison of p-side down and p-side up GaN light-emitting diodes fabricated by laser lift-off,” Jpn. J Appl. Phys. Part 2 Lett 42, 147–149 (2003).

J.-O. Song, D.-S. Leem, and T.-Y. Seong, “Formation of low resistance and transparent ohmic contacts to p-type GaN using Ni–Mg solid solution,” Appl. Phys. Lett. 83(17), 3513–3515 (2003).
[CrossRef]

H. W. Jang, S. Y. Kim, and J.-L. Lee, “Mechanism for ohmic contact formation of oxidized Ni/Au on p-type GaN,” J. Appl. Phys. 94(3), 1748–1750 (2003).
[CrossRef]

2002

H. W. Jang, J.-H. Lee, and J.-L. Lee, “Characterization of band bending on Ga-face and N-face GaN films grown by metalorganic chemical-vapor deposition,” Appl. Phys. Lett. 80(21), 3955–3957 (2002).
[CrossRef]

2001

J. S. Kwak, K. Y. Lee, J. Y. Han, J. Cho, S. Chae, O. H. Nam, and Y. Park, “Crystal-polarity dependence of Ti/Al contacts to freestanding n-GaN substrate,” Appl. Phys. Lett. 79(20), 3254–3256 (2001).
[CrossRef]

M. H. Kim, Y. C. Bang, N. M. Park, C. J. Choi, T.-Y. Seong, and S.-J. Park, “Growth of high-quality GaN on Si (111) substrate by UVCVD,” Appl. Phys. Lett. 78, 2858 (2001).
[CrossRef]

2000

V. Ramachandran, R. M. Feenstra, W. L. Sarney, L. Salamanca-Riba, and D. W. Greve, “Optimized structural properties of wurtzite GaN on SiC (0001) grown by molecular beam epitaxy,” J. Vac. Sci. Technol. A 18(4), 1915–1918 (2000).
[CrossRef]

U. Karrer, O. Ambacher, and M. Stutzmann, “Influence of crystal polarity on the properties of Pt/GaN Schottky diodes,” Appl. Phys. Lett. 77(13), 2012–2014 (2000).
[CrossRef]

I. Waki, H. Fujioka, K. Ono, M. Oshima, H. Miki, and A. Fukizawa, “The effect of surface cleaning by wet Treatments and ultra high vacuum annealing for ohmic contact formation of P-type GaN,” Jpn. J. Appl. Phys. 39(Part 1, No. 7B), 4451–4455 (2000).
[CrossRef]

1999

W. S. Wong, T. Sands, N. W. Cheung, M. Kneissl, D. P. Bour, P. Mei, L. T. Romano, and N. M. Johnson, “Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off,” Appl. Phys. Lett. 75(10), 1360–1362 (1999).
[CrossRef]

1998

J. K. Kim, J. L. Lee, J. W. Lee, H. E. Shin, Y. J. Park, and T. I. Kim, “Low resistance Pd/Au ohmic contacts to p-type GaN using surface treatment,” Appl. Phys. Lett. 73(20), 2953–2955 (1998).
[CrossRef]

1997

B. P. Luther, S. E. Mohney, T. N. Jackson, M. Asif Khan, Q. Chen, and J. W. Yang, “Investigation of the mechanism for Ohmic contact formation in Al and Ti/Al contacts to n -type GaN,” Appl. Phys. Lett. 70(1), 57–59 (1997).
[CrossRef]

1996

L. F. Lester, J. M. Brown, J. C. Ramer, L. Zhang, S. D. Hersee, and J. C. Zolper, “Nonalloyed Ti/Al ohmic contacts to n‐type GaN using high‐temperature premetallization anneal,” Appl. Phys. Lett. 69(18), 2737–2739 (1996).
[CrossRef]

1995

P. Boguslawski, E. L. Briggs, and J. Bernholc, “Native defects in gallium nitride,” Phys. Rev. B. 51(23), 17255–17258 (1995).
[CrossRef] [PubMed]

1994

M. E. Lin, Z. Ma, F. Y. Huang, Z. F. Fan, L. H. Allen, and H. Morkoç, “Low resistance ohmic contacts on wide band‐gap GaN,” Appl. Phys. Lett. 64(8), 1003 (1994).
[CrossRef]

Allen, L. H.

M. E. Lin, Z. Ma, F. Y. Huang, Z. F. Fan, L. H. Allen, and H. Morkoç, “Low resistance ohmic contacts on wide band‐gap GaN,” Appl. Phys. Lett. 64(8), 1003 (1994).
[CrossRef]

Ambacher, O.

U. Karrer, O. Ambacher, and M. Stutzmann, “Influence of crystal polarity on the properties of Pt/GaN Schottky diodes,” Appl. Phys. Lett. 77(13), 2012–2014 (2000).
[CrossRef]

Asif Khan, M.

B. P. Luther, S. E. Mohney, T. N. Jackson, M. Asif Khan, Q. Chen, and J. W. Yang, “Investigation of the mechanism for Ohmic contact formation in Al and Ti/Al contacts to n -type GaN,” Appl. Phys. Lett. 70(1), 57–59 (1997).
[CrossRef]

Bang, Y. C.

M. H. Kim, Y. C. Bang, N. M. Park, C. J. Choi, T.-Y. Seong, and S.-J. Park, “Growth of high-quality GaN on Si (111) substrate by UVCVD,” Appl. Phys. Lett. 78, 2858 (2001).
[CrossRef]

Bernholc, J.

P. Boguslawski, E. L. Briggs, and J. Bernholc, “Native defects in gallium nitride,” Phys. Rev. B. 51(23), 17255–17258 (1995).
[CrossRef] [PubMed]

Boguslawski, P.

P. Boguslawski, E. L. Briggs, and J. Bernholc, “Native defects in gallium nitride,” Phys. Rev. B. 51(23), 17255–17258 (1995).
[CrossRef] [PubMed]

Bour, D. P.

W. S. Wong, T. Sands, N. W. Cheung, M. Kneissl, D. P. Bour, P. Mei, L. T. Romano, and N. M. Johnson, “Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off,” Appl. Phys. Lett. 75(10), 1360–1362 (1999).
[CrossRef]

Briggs, E. L.

P. Boguslawski, E. L. Briggs, and J. Bernholc, “Native defects in gallium nitride,” Phys. Rev. B. 51(23), 17255–17258 (1995).
[CrossRef] [PubMed]

Brown, J. M.

L. F. Lester, J. M. Brown, J. C. Ramer, L. Zhang, S. D. Hersee, and J. C. Zolper, “Nonalloyed Ti/Al ohmic contacts to n‐type GaN using high‐temperature premetallization anneal,” Appl. Phys. Lett. 69(18), 2737–2739 (1996).
[CrossRef]

Chae, S.

J. S. Kwak, K. Y. Lee, J. Y. Han, J. Cho, S. Chae, O. H. Nam, and Y. Park, “Crystal-polarity dependence of Ti/Al contacts to freestanding n-GaN substrate,” Appl. Phys. Lett. 79(20), 3254–3256 (2001).
[CrossRef]

Chen, Q.

B. P. Luther, S. E. Mohney, T. N. Jackson, M. Asif Khan, Q. Chen, and J. W. Yang, “Investigation of the mechanism for Ohmic contact formation in Al and Ti/Al contacts to n -type GaN,” Appl. Phys. Lett. 70(1), 57–59 (1997).
[CrossRef]

Cheng, H. C.

C. F. Chu, C. C. Yu, H. C. Cheng, C. F. Lin, and S. C. Wang, “Comparison of p-side down and p-side up GaN light-emitting diodes fabricated by laser lift-off,” Jpn. J Appl. Phys. Part 2 Lett 42, 147–149 (2003).

Cheung, N. W.

W. S. Wong, T. Sands, N. W. Cheung, M. Kneissl, D. P. Bour, P. Mei, L. T. Romano, and N. M. Johnson, “Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off,” Appl. Phys. Lett. 75(10), 1360–1362 (1999).
[CrossRef]

Cho, J.

J. S. Kwak, K. Y. Lee, J. Y. Han, J. Cho, S. Chae, O. H. Nam, and Y. Park, “Crystal-polarity dependence of Ti/Al contacts to freestanding n-GaN substrate,” Appl. Phys. Lett. 79(20), 3254–3256 (2001).
[CrossRef]

Cho, M. W.

J. S. Ha, S. W. Lee, H. J. Lee, H.-J. Lee, S. H. Lee, H. Goto, T. Kato, K. Fujii, M. W. Cho, and T. Yao, “The fabrication of vertical LEDs using chemical lift-off process,” IEEE Photon. Technol. Lett. 20(3), 175–177 (2008).
[CrossRef]

Choi, C. J.

M. H. Kim, Y. C. Bang, N. M. Park, C. J. Choi, T.-Y. Seong, and S.-J. Park, “Growth of high-quality GaN on Si (111) substrate by UVCVD,” Appl. Phys. Lett. 78, 2858 (2001).
[CrossRef]

Choi, H. S.

S. Y. Lee, K. K. Choi, H.-H. Jeong, H. S. Choi, T.-H. Oh, J.-O. Song, and T.-Y. Seong, “Wafer-level fabrication of GaN-based vertical light-emitting diodes using a multi-functional bonding material system,” Semicond. Sci. Technol. 24(9), 092001 (2009).
[CrossRef]

Choi, K. K.

S. Y. Lee, K. K. Choi, H.-H. Jeong, H. S. Choi, T.-H. Oh, J.-O. Song, and T.-Y. Seong, “Wafer-level fabrication of GaN-based vertical light-emitting diodes using a multi-functional bonding material system,” Semicond. Sci. Technol. 24(9), 092001 (2009).
[CrossRef]

Chu, C. F.

C. F. Chu, C. C. Yu, H. C. Cheng, C. F. Lin, and S. C. Wang, “Comparison of p-side down and p-side up GaN light-emitting diodes fabricated by laser lift-off,” Jpn. J Appl. Phys. Part 2 Lett 42, 147–149 (2003).

Dupuis, R. D.

H. Kim, J.-H. Ryou, R. D. Dupuis, S.-N. Lee, Y. Park, J.-W. Jeon, and T.-Y. Seong, “Electrical characteristics of contacts to thin film N-polar n-type GaN,” Appl. Phys. Lett. 93(19), 192106 (2008).
[CrossRef]

Fan, Z. F.

M. E. Lin, Z. Ma, F. Y. Huang, Z. F. Fan, L. H. Allen, and H. Morkoç, “Low resistance ohmic contacts on wide band‐gap GaN,” Appl. Phys. Lett. 64(8), 1003 (1994).
[CrossRef]

Feenstra, R. M.

V. Ramachandran, R. M. Feenstra, W. L. Sarney, L. Salamanca-Riba, and D. W. Greve, “Optimized structural properties of wurtzite GaN on SiC (0001) grown by molecular beam epitaxy,” J. Vac. Sci. Technol. A 18(4), 1915–1918 (2000).
[CrossRef]

Fujii, K.

J. S. Ha, S. W. Lee, H. J. Lee, H.-J. Lee, S. H. Lee, H. Goto, T. Kato, K. Fujii, M. W. Cho, and T. Yao, “The fabrication of vertical LEDs using chemical lift-off process,” IEEE Photon. Technol. Lett. 20(3), 175–177 (2008).
[CrossRef]

Fujioka, H.

I. Waki, H. Fujioka, K. Ono, M. Oshima, H. Miki, and A. Fukizawa, “The effect of surface cleaning by wet Treatments and ultra high vacuum annealing for ohmic contact formation of P-type GaN,” Jpn. J. Appl. Phys. 39(Part 1, No. 7B), 4451–4455 (2000).
[CrossRef]

Fukizawa, A.

I. Waki, H. Fujioka, K. Ono, M. Oshima, H. Miki, and A. Fukizawa, “The effect of surface cleaning by wet Treatments and ultra high vacuum annealing for ohmic contact formation of P-type GaN,” Jpn. J. Appl. Phys. 39(Part 1, No. 7B), 4451–4455 (2000).
[CrossRef]

Goto, H.

J. S. Ha, S. W. Lee, H. J. Lee, H.-J. Lee, S. H. Lee, H. Goto, T. Kato, K. Fujii, M. W. Cho, and T. Yao, “The fabrication of vertical LEDs using chemical lift-off process,” IEEE Photon. Technol. Lett. 20(3), 175–177 (2008).
[CrossRef]

Greve, D. W.

V. Ramachandran, R. M. Feenstra, W. L. Sarney, L. Salamanca-Riba, and D. W. Greve, “Optimized structural properties of wurtzite GaN on SiC (0001) grown by molecular beam epitaxy,” J. Vac. Sci. Technol. A 18(4), 1915–1918 (2000).
[CrossRef]

Ha, J. S.

J. S. Ha, S. W. Lee, H. J. Lee, H.-J. Lee, S. H. Lee, H. Goto, T. Kato, K. Fujii, M. W. Cho, and T. Yao, “The fabrication of vertical LEDs using chemical lift-off process,” IEEE Photon. Technol. Lett. 20(3), 175–177 (2008).
[CrossRef]

Ha, J.-S.

J.-O. Song, J.-S. Ha, and T.-Y. Seong, “Ohmic contact technology for GaN-based LEDs: role of p-type Contact,” IEEE Trans. Electron. Dev. 57(1), 42–59 (2010).
[CrossRef]

Han, J. Y.

J. S. Kwak, K. Y. Lee, J. Y. Han, J. Cho, S. Chae, O. H. Nam, and Y. Park, “Crystal-polarity dependence of Ti/Al contacts to freestanding n-GaN substrate,” Appl. Phys. Lett. 79(20), 3254–3256 (2001).
[CrossRef]

Hersee, S. D.

L. F. Lester, J. M. Brown, J. C. Ramer, L. Zhang, S. D. Hersee, and J. C. Zolper, “Nonalloyed Ti/Al ohmic contacts to n‐type GaN using high‐temperature premetallization anneal,” Appl. Phys. Lett. 69(18), 2737–2739 (1996).
[CrossRef]

Huang, F. Y.

M. E. Lin, Z. Ma, F. Y. Huang, Z. F. Fan, L. H. Allen, and H. Morkoç, “Low resistance ohmic contacts on wide band‐gap GaN,” Appl. Phys. Lett. 64(8), 1003 (1994).
[CrossRef]

Jackson, T. N.

B. P. Luther, S. E. Mohney, T. N. Jackson, M. Asif Khan, Q. Chen, and J. W. Yang, “Investigation of the mechanism for Ohmic contact formation in Al and Ti/Al contacts to n -type GaN,” Appl. Phys. Lett. 70(1), 57–59 (1997).
[CrossRef]

Jang, H. W.

H. W. Jang, S. Y. Kim, and J.-L. Lee, “Mechanism for ohmic contact formation of oxidized Ni/Au on p-type GaN,” J. Appl. Phys. 94(3), 1748–1750 (2003).
[CrossRef]

H. W. Jang, J.-H. Lee, and J.-L. Lee, “Characterization of band bending on Ga-face and N-face GaN films grown by metalorganic chemical-vapor deposition,” Appl. Phys. Lett. 80(21), 3955–3957 (2002).
[CrossRef]

Jang, T.

T. Jang, S. N. Lee, O. H. Nam, and Y. Park, “Investigation of Pd/Ti/Al and Ti/Al ohmic contact materials on Ga-face and N-face surfaces of n-type GaN,” Appl. Phys. Lett. 88(19), 193505 (2006).
[CrossRef]

Jeon, J.-W.

J.-W. Jeon, S. Y. Lee, J.-O. Song, and T.-Y. Seong, “Highly reliable ohmic contacts to N-polar n-type GaN for vertical light-emitting diodes via laser-annealing,” IEEE Photon. Technol. Lett. 23, 1784–1786 (2011).
[CrossRef]

J.-W. Jeon, S.-H. Park, S.-Y. Jung, S. Y. Lee, J. Moon, J.-O. Song, and T.-Y. Seong, “Formation of low-resistance ohmic contacts to N-face n-GaN for high-power GaN-based vertical light-emitting diodes,” Appl. Phys. Lett. 97(9), 092103 (2010).
[CrossRef]

J.-W. Jeon, T.-Y. Seong, H. Kim, and K.-K. Kim, “TiN/Al ohmic contacts to N-face n-type GaN for high-performance vertical light-emitting diodes,” Appl. Phys. Lett. 94(4), 042102 (2009).
[CrossRef]

H. Kim, J.-H. Ryou, R. D. Dupuis, S.-N. Lee, Y. Park, J.-W. Jeon, and T.-Y. Seong, “Electrical characteristics of contacts to thin film N-polar n-type GaN,” Appl. Phys. Lett. 93(19), 192106 (2008).
[CrossRef]

Jeong, H.-H.

S. Y. Lee, K. K. Choi, H.-H. Jeong, H. S. Choi, T.-H. Oh, J.-O. Song, and T.-Y. Seong, “Wafer-level fabrication of GaN-based vertical light-emitting diodes using a multi-functional bonding material system,” Semicond. Sci. Technol. 24(9), 092001 (2009).
[CrossRef]

Johnson, N. M.

W. S. Wong, T. Sands, N. W. Cheung, M. Kneissl, D. P. Bour, P. Mei, L. T. Romano, and N. M. Johnson, “Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off,” Appl. Phys. Lett. 75(10), 1360–1362 (1999).
[CrossRef]

Jung, S.-Y.

J.-W. Jeon, S.-H. Park, S.-Y. Jung, S. Y. Lee, J. Moon, J.-O. Song, and T.-Y. Seong, “Formation of low-resistance ohmic contacts to N-face n-GaN for high-power GaN-based vertical light-emitting diodes,” Appl. Phys. Lett. 97(9), 092103 (2010).
[CrossRef]

Karrer, U.

U. Karrer, O. Ambacher, and M. Stutzmann, “Influence of crystal polarity on the properties of Pt/GaN Schottky diodes,” Appl. Phys. Lett. 77(13), 2012–2014 (2000).
[CrossRef]

Kato, T.

J. S. Ha, S. W. Lee, H. J. Lee, H.-J. Lee, S. H. Lee, H. Goto, T. Kato, K. Fujii, M. W. Cho, and T. Yao, “The fabrication of vertical LEDs using chemical lift-off process,” IEEE Photon. Technol. Lett. 20(3), 175–177 (2008).
[CrossRef]

Kim, H.

J.-W. Jeon, T.-Y. Seong, H. Kim, and K.-K. Kim, “TiN/Al ohmic contacts to N-face n-type GaN for high-performance vertical light-emitting diodes,” Appl. Phys. Lett. 94(4), 042102 (2009).
[CrossRef]

H. Kim, S.-N. Lee, Y. Park, J. S. Kwak, and T.-Y. Seong, “Metallization contacts to nonpolar a-plane n-type GaN,” Appl. Phys. Lett. 93(3), 032105 (2008).
[CrossRef]

H. Kim, J.-H. Ryou, R. D. Dupuis, S.-N. Lee, Y. Park, J.-W. Jeon, and T.-Y. Seong, “Electrical characteristics of contacts to thin film N-polar n-type GaN,” Appl. Phys. Lett. 93(19), 192106 (2008).
[CrossRef]

Kim, J. K.

J. K. Kim, J. L. Lee, J. W. Lee, H. E. Shin, Y. J. Park, and T. I. Kim, “Low resistance Pd/Au ohmic contacts to p-type GaN using surface treatment,” Appl. Phys. Lett. 73(20), 2953–2955 (1998).
[CrossRef]

Kim, K.-K.

J.-W. Jeon, T.-Y. Seong, H. Kim, and K.-K. Kim, “TiN/Al ohmic contacts to N-face n-type GaN for high-performance vertical light-emitting diodes,” Appl. Phys. Lett. 94(4), 042102 (2009).
[CrossRef]

Kim, M. H.

M. H. Kim, Y. C. Bang, N. M. Park, C. J. Choi, T.-Y. Seong, and S.-J. Park, “Growth of high-quality GaN on Si (111) substrate by UVCVD,” Appl. Phys. Lett. 78, 2858 (2001).
[CrossRef]

Kim, S. Y.

H. W. Jang, S. Y. Kim, and J.-L. Lee, “Mechanism for ohmic contact formation of oxidized Ni/Au on p-type GaN,” J. Appl. Phys. 94(3), 1748–1750 (2003).
[CrossRef]

Kim, T. I.

J. K. Kim, J. L. Lee, J. W. Lee, H. E. Shin, Y. J. Park, and T. I. Kim, “Low resistance Pd/Au ohmic contacts to p-type GaN using surface treatment,” Appl. Phys. Lett. 73(20), 2953–2955 (1998).
[CrossRef]

Kneissl, M.

W. S. Wong, T. Sands, N. W. Cheung, M. Kneissl, D. P. Bour, P. Mei, L. T. Romano, and N. M. Johnson, “Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off,” Appl. Phys. Lett. 75(10), 1360–1362 (1999).
[CrossRef]

Kwak, J. S.

H. Kim, S.-N. Lee, Y. Park, J. S. Kwak, and T.-Y. Seong, “Metallization contacts to nonpolar a-plane n-type GaN,” Appl. Phys. Lett. 93(3), 032105 (2008).
[CrossRef]

J. S. Kwak, K. Y. Lee, J. Y. Han, J. Cho, S. Chae, O. H. Nam, and Y. Park, “Crystal-polarity dependence of Ti/Al contacts to freestanding n-GaN substrate,” Appl. Phys. Lett. 79(20), 3254–3256 (2001).
[CrossRef]

Lee, H. J.

J. S. Ha, S. W. Lee, H. J. Lee, H.-J. Lee, S. H. Lee, H. Goto, T. Kato, K. Fujii, M. W. Cho, and T. Yao, “The fabrication of vertical LEDs using chemical lift-off process,” IEEE Photon. Technol. Lett. 20(3), 175–177 (2008).
[CrossRef]

Lee, H.-J.

J. S. Ha, S. W. Lee, H. J. Lee, H.-J. Lee, S. H. Lee, H. Goto, T. Kato, K. Fujii, M. W. Cho, and T. Yao, “The fabrication of vertical LEDs using chemical lift-off process,” IEEE Photon. Technol. Lett. 20(3), 175–177 (2008).
[CrossRef]

Lee, J. L.

J. K. Kim, J. L. Lee, J. W. Lee, H. E. Shin, Y. J. Park, and T. I. Kim, “Low resistance Pd/Au ohmic contacts to p-type GaN using surface treatment,” Appl. Phys. Lett. 73(20), 2953–2955 (1998).
[CrossRef]

Lee, J. W.

J. K. Kim, J. L. Lee, J. W. Lee, H. E. Shin, Y. J. Park, and T. I. Kim, “Low resistance Pd/Au ohmic contacts to p-type GaN using surface treatment,” Appl. Phys. Lett. 73(20), 2953–2955 (1998).
[CrossRef]

Lee, J.-H.

H. W. Jang, J.-H. Lee, and J.-L. Lee, “Characterization of band bending on Ga-face and N-face GaN films grown by metalorganic chemical-vapor deposition,” Appl. Phys. Lett. 80(21), 3955–3957 (2002).
[CrossRef]

Lee, J.-L.

H. W. Jang, S. Y. Kim, and J.-L. Lee, “Mechanism for ohmic contact formation of oxidized Ni/Au on p-type GaN,” J. Appl. Phys. 94(3), 1748–1750 (2003).
[CrossRef]

H. W. Jang, J.-H. Lee, and J.-L. Lee, “Characterization of band bending on Ga-face and N-face GaN films grown by metalorganic chemical-vapor deposition,” Appl. Phys. Lett. 80(21), 3955–3957 (2002).
[CrossRef]

Lee, K. Y.

J. S. Kwak, K. Y. Lee, J. Y. Han, J. Cho, S. Chae, O. H. Nam, and Y. Park, “Crystal-polarity dependence of Ti/Al contacts to freestanding n-GaN substrate,” Appl. Phys. Lett. 79(20), 3254–3256 (2001).
[CrossRef]

Lee, S. H.

J. S. Ha, S. W. Lee, H. J. Lee, H.-J. Lee, S. H. Lee, H. Goto, T. Kato, K. Fujii, M. W. Cho, and T. Yao, “The fabrication of vertical LEDs using chemical lift-off process,” IEEE Photon. Technol. Lett. 20(3), 175–177 (2008).
[CrossRef]

Lee, S. N.

T. Jang, S. N. Lee, O. H. Nam, and Y. Park, “Investigation of Pd/Ti/Al and Ti/Al ohmic contact materials on Ga-face and N-face surfaces of n-type GaN,” Appl. Phys. Lett. 88(19), 193505 (2006).
[CrossRef]

Lee, S. W.

J. S. Ha, S. W. Lee, H. J. Lee, H.-J. Lee, S. H. Lee, H. Goto, T. Kato, K. Fujii, M. W. Cho, and T. Yao, “The fabrication of vertical LEDs using chemical lift-off process,” IEEE Photon. Technol. Lett. 20(3), 175–177 (2008).
[CrossRef]

Lee, S. Y.

J.-W. Jeon, S. Y. Lee, J.-O. Song, and T.-Y. Seong, “Highly reliable ohmic contacts to N-polar n-type GaN for vertical light-emitting diodes via laser-annealing,” IEEE Photon. Technol. Lett. 23, 1784–1786 (2011).
[CrossRef]

J.-W. Jeon, S.-H. Park, S.-Y. Jung, S. Y. Lee, J. Moon, J.-O. Song, and T.-Y. Seong, “Formation of low-resistance ohmic contacts to N-face n-GaN for high-power GaN-based vertical light-emitting diodes,” Appl. Phys. Lett. 97(9), 092103 (2010).
[CrossRef]

S. Y. Lee, K. K. Choi, H.-H. Jeong, H. S. Choi, T.-H. Oh, J.-O. Song, and T.-Y. Seong, “Wafer-level fabrication of GaN-based vertical light-emitting diodes using a multi-functional bonding material system,” Semicond. Sci. Technol. 24(9), 092001 (2009).
[CrossRef]

Lee, S.-N.

H. Kim, J.-H. Ryou, R. D. Dupuis, S.-N. Lee, Y. Park, J.-W. Jeon, and T.-Y. Seong, “Electrical characteristics of contacts to thin film N-polar n-type GaN,” Appl. Phys. Lett. 93(19), 192106 (2008).
[CrossRef]

H. Kim, S.-N. Lee, Y. Park, J. S. Kwak, and T.-Y. Seong, “Metallization contacts to nonpolar a-plane n-type GaN,” Appl. Phys. Lett. 93(3), 032105 (2008).
[CrossRef]

Leem, D.-S.

J.-O. Song, D.-S. Leem, and T.-Y. Seong, “Formation of low resistance and transparent ohmic contacts to p-type GaN using Ni–Mg solid solution,” Appl. Phys. Lett. 83(17), 3513–3515 (2003).
[CrossRef]

Lester, L. F.

L. F. Lester, J. M. Brown, J. C. Ramer, L. Zhang, S. D. Hersee, and J. C. Zolper, “Nonalloyed Ti/Al ohmic contacts to n‐type GaN using high‐temperature premetallization anneal,” Appl. Phys. Lett. 69(18), 2737–2739 (1996).
[CrossRef]

Lin, C. F.

C. F. Chu, C. C. Yu, H. C. Cheng, C. F. Lin, and S. C. Wang, “Comparison of p-side down and p-side up GaN light-emitting diodes fabricated by laser lift-off,” Jpn. J Appl. Phys. Part 2 Lett 42, 147–149 (2003).

Lin, M. E.

M. E. Lin, Z. Ma, F. Y. Huang, Z. F. Fan, L. H. Allen, and H. Morkoç, “Low resistance ohmic contacts on wide band‐gap GaN,” Appl. Phys. Lett. 64(8), 1003 (1994).
[CrossRef]

Luther, B. P.

B. P. Luther, S. E. Mohney, T. N. Jackson, M. Asif Khan, Q. Chen, and J. W. Yang, “Investigation of the mechanism for Ohmic contact formation in Al and Ti/Al contacts to n -type GaN,” Appl. Phys. Lett. 70(1), 57–59 (1997).
[CrossRef]

Ma, Z.

M. E. Lin, Z. Ma, F. Y. Huang, Z. F. Fan, L. H. Allen, and H. Morkoç, “Low resistance ohmic contacts on wide band‐gap GaN,” Appl. Phys. Lett. 64(8), 1003 (1994).
[CrossRef]

Mei, P.

W. S. Wong, T. Sands, N. W. Cheung, M. Kneissl, D. P. Bour, P. Mei, L. T. Romano, and N. M. Johnson, “Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off,” Appl. Phys. Lett. 75(10), 1360–1362 (1999).
[CrossRef]

Miki, H.

I. Waki, H. Fujioka, K. Ono, M. Oshima, H. Miki, and A. Fukizawa, “The effect of surface cleaning by wet Treatments and ultra high vacuum annealing for ohmic contact formation of P-type GaN,” Jpn. J. Appl. Phys. 39(Part 1, No. 7B), 4451–4455 (2000).
[CrossRef]

Mohney, S. E.

B. P. Luther, S. E. Mohney, T. N. Jackson, M. Asif Khan, Q. Chen, and J. W. Yang, “Investigation of the mechanism for Ohmic contact formation in Al and Ti/Al contacts to n -type GaN,” Appl. Phys. Lett. 70(1), 57–59 (1997).
[CrossRef]

Moon, J.

J.-W. Jeon, S.-H. Park, S.-Y. Jung, S. Y. Lee, J. Moon, J.-O. Song, and T.-Y. Seong, “Formation of low-resistance ohmic contacts to N-face n-GaN for high-power GaN-based vertical light-emitting diodes,” Appl. Phys. Lett. 97(9), 092103 (2010).
[CrossRef]

Morkoç, H.

M. E. Lin, Z. Ma, F. Y. Huang, Z. F. Fan, L. H. Allen, and H. Morkoç, “Low resistance ohmic contacts on wide band‐gap GaN,” Appl. Phys. Lett. 64(8), 1003 (1994).
[CrossRef]

Nam, O. H.

T. Jang, S. N. Lee, O. H. Nam, and Y. Park, “Investigation of Pd/Ti/Al and Ti/Al ohmic contact materials on Ga-face and N-face surfaces of n-type GaN,” Appl. Phys. Lett. 88(19), 193505 (2006).
[CrossRef]

J. S. Kwak, K. Y. Lee, J. Y. Han, J. Cho, S. Chae, O. H. Nam, and Y. Park, “Crystal-polarity dependence of Ti/Al contacts to freestanding n-GaN substrate,” Appl. Phys. Lett. 79(20), 3254–3256 (2001).
[CrossRef]

Oh, T.-H.

S. Y. Lee, K. K. Choi, H.-H. Jeong, H. S. Choi, T.-H. Oh, J.-O. Song, and T.-Y. Seong, “Wafer-level fabrication of GaN-based vertical light-emitting diodes using a multi-functional bonding material system,” Semicond. Sci. Technol. 24(9), 092001 (2009).
[CrossRef]

Ono, K.

I. Waki, H. Fujioka, K. Ono, M. Oshima, H. Miki, and A. Fukizawa, “The effect of surface cleaning by wet Treatments and ultra high vacuum annealing for ohmic contact formation of P-type GaN,” Jpn. J. Appl. Phys. 39(Part 1, No. 7B), 4451–4455 (2000).
[CrossRef]

Oshima, M.

I. Waki, H. Fujioka, K. Ono, M. Oshima, H. Miki, and A. Fukizawa, “The effect of surface cleaning by wet Treatments and ultra high vacuum annealing for ohmic contact formation of P-type GaN,” Jpn. J. Appl. Phys. 39(Part 1, No. 7B), 4451–4455 (2000).
[CrossRef]

Park, N. M.

M. H. Kim, Y. C. Bang, N. M. Park, C. J. Choi, T.-Y. Seong, and S.-J. Park, “Growth of high-quality GaN on Si (111) substrate by UVCVD,” Appl. Phys. Lett. 78, 2858 (2001).
[CrossRef]

Park, S.-H.

J.-W. Jeon, S.-H. Park, S.-Y. Jung, S. Y. Lee, J. Moon, J.-O. Song, and T.-Y. Seong, “Formation of low-resistance ohmic contacts to N-face n-GaN for high-power GaN-based vertical light-emitting diodes,” Appl. Phys. Lett. 97(9), 092103 (2010).
[CrossRef]

Park, S.-J.

M. H. Kim, Y. C. Bang, N. M. Park, C. J. Choi, T.-Y. Seong, and S.-J. Park, “Growth of high-quality GaN on Si (111) substrate by UVCVD,” Appl. Phys. Lett. 78, 2858 (2001).
[CrossRef]

Park, Y.

H. Kim, S.-N. Lee, Y. Park, J. S. Kwak, and T.-Y. Seong, “Metallization contacts to nonpolar a-plane n-type GaN,” Appl. Phys. Lett. 93(3), 032105 (2008).
[CrossRef]

H. Kim, J.-H. Ryou, R. D. Dupuis, S.-N. Lee, Y. Park, J.-W. Jeon, and T.-Y. Seong, “Electrical characteristics of contacts to thin film N-polar n-type GaN,” Appl. Phys. Lett. 93(19), 192106 (2008).
[CrossRef]

T. Jang, S. N. Lee, O. H. Nam, and Y. Park, “Investigation of Pd/Ti/Al and Ti/Al ohmic contact materials on Ga-face and N-face surfaces of n-type GaN,” Appl. Phys. Lett. 88(19), 193505 (2006).
[CrossRef]

J. S. Kwak, K. Y. Lee, J. Y. Han, J. Cho, S. Chae, O. H. Nam, and Y. Park, “Crystal-polarity dependence of Ti/Al contacts to freestanding n-GaN substrate,” Appl. Phys. Lett. 79(20), 3254–3256 (2001).
[CrossRef]

Park, Y. J.

J. K. Kim, J. L. Lee, J. W. Lee, H. E. Shin, Y. J. Park, and T. I. Kim, “Low resistance Pd/Au ohmic contacts to p-type GaN using surface treatment,” Appl. Phys. Lett. 73(20), 2953–2955 (1998).
[CrossRef]

Ramachandran, V.

V. Ramachandran, R. M. Feenstra, W. L. Sarney, L. Salamanca-Riba, and D. W. Greve, “Optimized structural properties of wurtzite GaN on SiC (0001) grown by molecular beam epitaxy,” J. Vac. Sci. Technol. A 18(4), 1915–1918 (2000).
[CrossRef]

Ramer, J. C.

L. F. Lester, J. M. Brown, J. C. Ramer, L. Zhang, S. D. Hersee, and J. C. Zolper, “Nonalloyed Ti/Al ohmic contacts to n‐type GaN using high‐temperature premetallization anneal,” Appl. Phys. Lett. 69(18), 2737–2739 (1996).
[CrossRef]

Romano, L. T.

W. S. Wong, T. Sands, N. W. Cheung, M. Kneissl, D. P. Bour, P. Mei, L. T. Romano, and N. M. Johnson, “Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off,” Appl. Phys. Lett. 75(10), 1360–1362 (1999).
[CrossRef]

Ryou, J.-H.

H. Kim, J.-H. Ryou, R. D. Dupuis, S.-N. Lee, Y. Park, J.-W. Jeon, and T.-Y. Seong, “Electrical characteristics of contacts to thin film N-polar n-type GaN,” Appl. Phys. Lett. 93(19), 192106 (2008).
[CrossRef]

Salamanca-Riba, L.

V. Ramachandran, R. M. Feenstra, W. L. Sarney, L. Salamanca-Riba, and D. W. Greve, “Optimized structural properties of wurtzite GaN on SiC (0001) grown by molecular beam epitaxy,” J. Vac. Sci. Technol. A 18(4), 1915–1918 (2000).
[CrossRef]

Sands, T.

W. S. Wong, T. Sands, N. W. Cheung, M. Kneissl, D. P. Bour, P. Mei, L. T. Romano, and N. M. Johnson, “Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off,” Appl. Phys. Lett. 75(10), 1360–1362 (1999).
[CrossRef]

Sarney, W. L.

V. Ramachandran, R. M. Feenstra, W. L. Sarney, L. Salamanca-Riba, and D. W. Greve, “Optimized structural properties of wurtzite GaN on SiC (0001) grown by molecular beam epitaxy,” J. Vac. Sci. Technol. A 18(4), 1915–1918 (2000).
[CrossRef]

Seong, T.-Y.

J.-W. Jeon, S. Y. Lee, J.-O. Song, and T.-Y. Seong, “Highly reliable ohmic contacts to N-polar n-type GaN for vertical light-emitting diodes via laser-annealing,” IEEE Photon. Technol. Lett. 23, 1784–1786 (2011).
[CrossRef]

J.-O. Song, J.-S. Ha, and T.-Y. Seong, “Ohmic contact technology for GaN-based LEDs: role of p-type Contact,” IEEE Trans. Electron. Dev. 57(1), 42–59 (2010).
[CrossRef]

J.-W. Jeon, S.-H. Park, S.-Y. Jung, S. Y. Lee, J. Moon, J.-O. Song, and T.-Y. Seong, “Formation of low-resistance ohmic contacts to N-face n-GaN for high-power GaN-based vertical light-emitting diodes,” Appl. Phys. Lett. 97(9), 092103 (2010).
[CrossRef]

J.-W. Jeon, T.-Y. Seong, H. Kim, and K.-K. Kim, “TiN/Al ohmic contacts to N-face n-type GaN for high-performance vertical light-emitting diodes,” Appl. Phys. Lett. 94(4), 042102 (2009).
[CrossRef]

S. Y. Lee, K. K. Choi, H.-H. Jeong, H. S. Choi, T.-H. Oh, J.-O. Song, and T.-Y. Seong, “Wafer-level fabrication of GaN-based vertical light-emitting diodes using a multi-functional bonding material system,” Semicond. Sci. Technol. 24(9), 092001 (2009).
[CrossRef]

H. Kim, J.-H. Ryou, R. D. Dupuis, S.-N. Lee, Y. Park, J.-W. Jeon, and T.-Y. Seong, “Electrical characteristics of contacts to thin film N-polar n-type GaN,” Appl. Phys. Lett. 93(19), 192106 (2008).
[CrossRef]

H. Kim, S.-N. Lee, Y. Park, J. S. Kwak, and T.-Y. Seong, “Metallization contacts to nonpolar a-plane n-type GaN,” Appl. Phys. Lett. 93(3), 032105 (2008).
[CrossRef]

J.-O. Song, D.-S. Leem, and T.-Y. Seong, “Formation of low resistance and transparent ohmic contacts to p-type GaN using Ni–Mg solid solution,” Appl. Phys. Lett. 83(17), 3513–3515 (2003).
[CrossRef]

M. H. Kim, Y. C. Bang, N. M. Park, C. J. Choi, T.-Y. Seong, and S.-J. Park, “Growth of high-quality GaN on Si (111) substrate by UVCVD,” Appl. Phys. Lett. 78, 2858 (2001).
[CrossRef]

Shin, H. E.

J. K. Kim, J. L. Lee, J. W. Lee, H. E. Shin, Y. J. Park, and T. I. Kim, “Low resistance Pd/Au ohmic contacts to p-type GaN using surface treatment,” Appl. Phys. Lett. 73(20), 2953–2955 (1998).
[CrossRef]

Song, J.-O.

J.-W. Jeon, S. Y. Lee, J.-O. Song, and T.-Y. Seong, “Highly reliable ohmic contacts to N-polar n-type GaN for vertical light-emitting diodes via laser-annealing,” IEEE Photon. Technol. Lett. 23, 1784–1786 (2011).
[CrossRef]

J.-O. Song, J.-S. Ha, and T.-Y. Seong, “Ohmic contact technology for GaN-based LEDs: role of p-type Contact,” IEEE Trans. Electron. Dev. 57(1), 42–59 (2010).
[CrossRef]

J.-W. Jeon, S.-H. Park, S.-Y. Jung, S. Y. Lee, J. Moon, J.-O. Song, and T.-Y. Seong, “Formation of low-resistance ohmic contacts to N-face n-GaN for high-power GaN-based vertical light-emitting diodes,” Appl. Phys. Lett. 97(9), 092103 (2010).
[CrossRef]

S. Y. Lee, K. K. Choi, H.-H. Jeong, H. S. Choi, T.-H. Oh, J.-O. Song, and T.-Y. Seong, “Wafer-level fabrication of GaN-based vertical light-emitting diodes using a multi-functional bonding material system,” Semicond. Sci. Technol. 24(9), 092001 (2009).
[CrossRef]

J.-O. Song, D.-S. Leem, and T.-Y. Seong, “Formation of low resistance and transparent ohmic contacts to p-type GaN using Ni–Mg solid solution,” Appl. Phys. Lett. 83(17), 3513–3515 (2003).
[CrossRef]

Stutzmann, M.

U. Karrer, O. Ambacher, and M. Stutzmann, “Influence of crystal polarity on the properties of Pt/GaN Schottky diodes,” Appl. Phys. Lett. 77(13), 2012–2014 (2000).
[CrossRef]

Waki, I.

I. Waki, H. Fujioka, K. Ono, M. Oshima, H. Miki, and A. Fukizawa, “The effect of surface cleaning by wet Treatments and ultra high vacuum annealing for ohmic contact formation of P-type GaN,” Jpn. J. Appl. Phys. 39(Part 1, No. 7B), 4451–4455 (2000).
[CrossRef]

Wang, S. C.

C. F. Chu, C. C. Yu, H. C. Cheng, C. F. Lin, and S. C. Wang, “Comparison of p-side down and p-side up GaN light-emitting diodes fabricated by laser lift-off,” Jpn. J Appl. Phys. Part 2 Lett 42, 147–149 (2003).

Wong, W. S.

W. S. Wong, T. Sands, N. W. Cheung, M. Kneissl, D. P. Bour, P. Mei, L. T. Romano, and N. M. Johnson, “Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off,” Appl. Phys. Lett. 75(10), 1360–1362 (1999).
[CrossRef]

Yang, J. W.

B. P. Luther, S. E. Mohney, T. N. Jackson, M. Asif Khan, Q. Chen, and J. W. Yang, “Investigation of the mechanism for Ohmic contact formation in Al and Ti/Al contacts to n -type GaN,” Appl. Phys. Lett. 70(1), 57–59 (1997).
[CrossRef]

Yao, T.

J. S. Ha, S. W. Lee, H. J. Lee, H.-J. Lee, S. H. Lee, H. Goto, T. Kato, K. Fujii, M. W. Cho, and T. Yao, “The fabrication of vertical LEDs using chemical lift-off process,” IEEE Photon. Technol. Lett. 20(3), 175–177 (2008).
[CrossRef]

Yu, C. C.

C. F. Chu, C. C. Yu, H. C. Cheng, C. F. Lin, and S. C. Wang, “Comparison of p-side down and p-side up GaN light-emitting diodes fabricated by laser lift-off,” Jpn. J Appl. Phys. Part 2 Lett 42, 147–149 (2003).

Zhang, L.

L. F. Lester, J. M. Brown, J. C. Ramer, L. Zhang, S. D. Hersee, and J. C. Zolper, “Nonalloyed Ti/Al ohmic contacts to n‐type GaN using high‐temperature premetallization anneal,” Appl. Phys. Lett. 69(18), 2737–2739 (1996).
[CrossRef]

Zolper, J. C.

L. F. Lester, J. M. Brown, J. C. Ramer, L. Zhang, S. D. Hersee, and J. C. Zolper, “Nonalloyed Ti/Al ohmic contacts to n‐type GaN using high‐temperature premetallization anneal,” Appl. Phys. Lett. 69(18), 2737–2739 (1996).
[CrossRef]

Appl. Phys. Lett.

B. P. Luther, S. E. Mohney, T. N. Jackson, M. Asif Khan, Q. Chen, and J. W. Yang, “Investigation of the mechanism for Ohmic contact formation in Al and Ti/Al contacts to n -type GaN,” Appl. Phys. Lett. 70(1), 57–59 (1997).
[CrossRef]

M. E. Lin, Z. Ma, F. Y. Huang, Z. F. Fan, L. H. Allen, and H. Morkoç, “Low resistance ohmic contacts on wide band‐gap GaN,” Appl. Phys. Lett. 64(8), 1003 (1994).
[CrossRef]

L. F. Lester, J. M. Brown, J. C. Ramer, L. Zhang, S. D. Hersee, and J. C. Zolper, “Nonalloyed Ti/Al ohmic contacts to n‐type GaN using high‐temperature premetallization anneal,” Appl. Phys. Lett. 69(18), 2737–2739 (1996).
[CrossRef]

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Figures (4)

Fig. 1
Fig. 1

The typical I-V characteristics of Ti(10 nm)/Al(150 nm)/Au(30 nm) and Ti(10 nm)/Ta(10 nm)/Al(150 nm)/Au(30 nm) contacts on N-polar n-GaN as a function of annealing time at 250 °C.

Fig. 2
Fig. 2

The light output of LEDs fabricated with Ti/Al/Au and Ti/Ta/Al/Au contacts as a function of the forward current.

Fig. 3
Fig. 3

The Ga 2p core levels taken from the contact/GaN interface regions of (a) Ti/Al/Au and (b) Ti/Ta/Al/Au samples before and after annealing at 250 °C for 600 min.

Fig. 4
Fig. 4

XPS depth profiles obtained from (a) and (b) Ti/Al/Au, and (c) and (d) Ti/Ta/Al/Au samples on GaN before and after annealing at 250 °C for 600 min, respectively.

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