Abstract

AlGaN-based vertical type high power ultraviolet-C light emitting diodes (UV-C LEDs), which have a Ga-face n-contact structure, were fabricated on a LED epilayer transferred to a carrier wafer through a laser lift-off (LLO) process. A significant light extraction enhancement of the vertical chip by using a highly reflective ITO/Al p-type electrode is demonstrated, along with surface roughening. A GaN-free LED epi structure is employed to prevent light absorption in the UV-C wavelength region. The vertical chip with the ITO/Al reflector and n-AlGaN surface roughening exhibited a high light output power of 104.4mW with a peak wavelength of 277.6nm at an injection current of 350mA. Comparing the device characteristics of the vertical chip and the flip chip showed that the light output power of the vertical chip was 1.31 times higher than that of the flip chip at 350mA. In particular, with the high power vertical type UV-C LED, a maximum light output power of 630mW could be achieved at a current of 3.5A, and this is mainly attributed to efficient heat dissipation through a metal substrate and the resulting relatively lower junction temperature of the vertical chip.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

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References

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    [Crossref]
  7. L. Zhou, J. E. Epler, M. R. Krames, W. Goets, M. Gherasimova, Z. Ren, J. Han, M. Kneissl, and N. M. Johnson, “Vertical injection thin-film AlGaN/AlGaN multiple-quantum-well deep ultraviolet light-emitting diodes,” Appl. Phys. Lett. 89(24), 241113 (2006).
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    [Crossref]
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    [Crossref]
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    [Crossref]
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    [Crossref]
  19. V. Adivarahan, A. Heidari, B. Zhang, Q. Fareed, M. Islam, S. Hwang, K. Balakirshnan, and A. Khan, “Vertical Injection Thin Film Deep Ultraviolet Light Emitting Diodes with AlGaN Multiple-Quantum Wells Active Region,” Appl. Phys. Express 2(9), 092102 (2009).
    [Crossref]
  20. M. Lachab, F. Asif, B. Zhang, I. Ahmad, A. Heidari, Q. Fareed, V. Adivarahan, and A. Khan, “Enhancement of light extraction efficiency in sub-300 nm nitride thin-film flip-chip light-emitting diodes,” Solid-State Electron. 89, 156–160 (2013).
    [Crossref]
  21. S. K. Saha, R. S. Howell, and M. K. Hatalis, “Reaction Mechanisms in Aluminum-Indium Tin Oxide Ohmic Contact Metallization with Co and Ni Barrier Layers for Active-Matrix-Display Applications,” J. Electrochem. Soc. 146(8), 3134–3138 (1999).
    [Crossref]
  22. C. S. Chang, S. J. Chang, Y. K. Su, Y. C. Lin, Y. P. Hsu, S. C. Shei, S. C. Chen, C. H. Liu, and U. H. Liaw, “InGaN/GaN light emitting diodes with ITO p-contact layers prepared by RF sputteing,” Semicond. Sci. Technol. 18(4), L21–L23 (2003).
    [Crossref]
  23. T. Margalith, O. Buchinsky, D. A. Cohen, A. C. Abare, M. Hansen, S. P. DenBaars, and L. A. Coldren, “Indium tin oxide contacts to gallium nitride optoelectronic devices,” Appl. Phys. Lett. 74(26), 3930–3932 (1999).
    [Crossref]
  24. E. Fred Schubert, Light-Emitting Diodes II (Cambridge University Press, 2006).
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    [Crossref]
  26. C. Lu, L. Wang, J. Lu, R. Li, L. Liu, D. Li, N. Liu, L. Li, W. Cao, W. Yang, W. Chen, W. Du, C. T. Lee, and X. Hu, “Investigation of the electroluminescence spectrum shift of InGaN/GaN multiple quantum well light-emitting diodes under direct and pulsed currents,” J. Appl. Phys. 113(1), 013102 (2013).
    [Crossref]
  27. T. Nishida, T. Makimoto, H. Saito, and T. Ban, “AlGaN-based ultraviolet light-emitting diodes grown on bulk AlN substrates,” Appl. Phys. Lett. 84(6), 1002–1003 (2004).
    [Crossref]
  28. D. Priante, R. T. Elafandy, A. Prabaswara, B. Janjua, C. Zhao, M. S. Alias, M. Tangi, Y. Alaskar, A. M. Albadri, A. Y. Alyamani, T. K. Ng, and B. S. Ooi, “Diode junction temperature in ultraviolet AlGaN quantum-disks-in-nanowires,” J. Appl. Phys. 124(1), 015702 (2018).
    [Crossref]

2018 (2)

N. Maeda, J. Yum, M. Jo, and H. Hirayama, “Enhancing the light-extraction efficiency of AlGaN deep-ultraviolet light-emitting diodes using highly reflective Ni/Mg and Rh as p-type electrodes,” Jpn. J. Appl. Phys. 57(4S), 04FH08 (2018).
[Crossref]

D. Priante, R. T. Elafandy, A. Prabaswara, B. Janjua, C. Zhao, M. S. Alias, M. Tangi, Y. Alaskar, A. M. Albadri, A. Y. Alyamani, T. K. Ng, and B. S. Ooi, “Diode junction temperature in ultraviolet AlGaN quantum-disks-in-nanowires,” J. Appl. Phys. 124(1), 015702 (2018).
[Crossref]

2017 (2)

Y. Guo, Y. Zhang, J. Yan, H. Xie, L. Liu, X. Chen, M. Hou, Z. Qin, J. Wang, and J. Li, “Light extraction enhancement of AlGaN-based ultraviolet light-emitting diodes by substrate sidewall roughening,” Appl. Phys. Lett. 111(1), 011102 (2017).
[Crossref]

T. Takano, T. Mino, J. Sakai, N. Noguchi, K. Tsubaki, and H. Hirayama, “Deep-ultraviolet light-emitting diodes with external quantum efficiency higher than 20% at 275 nm achieved by improving light-extraction efficiency,” Appl. Phys. Express 10(3), 031002 (2017).
[Crossref]

2015 (1)

Z. Bryan, I. Bryan, J. Xie, S. Mita, Z. Sitar, and R. Collazo, “High internal quantum efficiency in AlGaN multiple quantum wells grown on bulk AlN substrates,” Appl. Phys. Lett. 106(14), 142107 (2015).
[Crossref]

2014 (1)

H. Hirayama, N. Maeda, S. Fujikawa, S. Toyoda, and N. Kamata, “Recent progress and future prospects of AlGaN-based high-efficiency deep-ultraviolet light-emitting diodes,” Jpn. J. Appl. Phys. 53(10), 100209 (2014).
[Crossref]

2013 (3)

P. Dong, J. Yan, J. Wang, Y. Zhang, C. Geng, T. Wei, P. Cong, Y. Zhang, J. Zeng, Y. Tian, L. Sung, Q. Yan, J. Li, S. Fan, and Z. Qin, “282-nm AlGaN-based deep ultraviolet light-emitting diodes with improved performance on nano-patterned sapphire substrates,” Appl. Phys. Lett. 102(24), 241113 (2013).
[Crossref]

M. Lachab, F. Asif, B. Zhang, I. Ahmad, A. Heidari, Q. Fareed, V. Adivarahan, and A. Khan, “Enhancement of light extraction efficiency in sub-300 nm nitride thin-film flip-chip light-emitting diodes,” Solid-State Electron. 89, 156–160 (2013).
[Crossref]

C. Lu, L. Wang, J. Lu, R. Li, L. Liu, D. Li, N. Liu, L. Li, W. Cao, W. Yang, W. Chen, W. Du, C. T. Lee, and X. Hu, “Investigation of the electroluminescence spectrum shift of InGaN/GaN multiple quantum well light-emitting diodes under direct and pulsed currents,” J. Appl. Phys. 113(1), 013102 (2013).
[Crossref]

2012 (1)

K. Takehara, K. Takeda, S. Ito, H. Aoshima, M. Iwaya, T. Takeuchi, S. Kamiyama, I. Akasaki, and H. Amano, “Indium–Tin Oxide/Al reflective electrodes for ultraviolet light-emitting diodes,” Jpn. J. Appl. Phys. 51(4R), 042101 (2012).
[Crossref]

2011 (2)

K. Ban, J.-i. Yamamoto, K. Takeda, K. Ide, M. Iwaya, T. Takeuchi, S. Kamiyama, I. Akasaki, and H. Amano, “Internal quantum efficiency of whole-composition-range AlGaN multi quantum wells,” Appl. Phys. Express 4(5), 052101 (2011).
[Crossref]

M. Kneissl, T. Kolbe, C. Chua, V. Kueller, N. Lobo, J. Stellmach, A. Knauer, H. Rodriguez, S. Einfeldt, and Z. Yang, “Advances in group III-nitride-based deep UV light-emitting diode technology,” Semicond. Sci. Technol. 26(1), 014036 (2011).
[Crossref]

2009 (2)

M. Takeuchi, T. Maegawa, H. Shimizu, S. Ooishi, T. Ohtsuka, and Y. Aoyagi, “AlN/AlGaN short-period superlattice sacrificial layers in laser lift-off for vertical-type AlGaN-based deep ultraviolet light emitting diodes,” Appl. Phys. Lett. 94(6), 061117 (2009).
[Crossref]

V. Adivarahan, A. Heidari, B. Zhang, Q. Fareed, M. Islam, S. Hwang, K. Balakirshnan, and A. Khan, “Vertical Injection Thin Film Deep Ultraviolet Light Emitting Diodes with AlGaN Multiple-Quantum Wells Active Region,” Appl. Phys. Express 2(9), 092102 (2009).
[Crossref]

2008 (2)

A. Khan, K. Balakrishnan, and T. Katona, “Ultraviolet light-emitting diodes based on group three nitrides,” Nat. Photonics 2(2), 77–84 (2008).
[Crossref]

R. H. Horng, X. Zheng, C. Y. Hsieh, and D. S. Wuu, “Light extraction enhancement of InGaN light-emitting diode by roughening both undoped micropillar-structure GaN and p-GaN as well as employing an omnidirectional reflector,” Appl. Phys. Lett. 93(2), 021125 (2008).
[Crossref]

2006 (2)

L. Zhou, J. E. Epler, M. R. Krames, W. Goets, M. Gherasimova, Z. Ren, J. Han, M. Kneissl, and N. M. Johnson, “Vertical injection thin-film AlGaN/AlGaN multiple-quantum-well deep ultraviolet light-emitting diodes,” Appl. Phys. Lett. 89(24), 241113 (2006).
[Crossref]

K. Kawasaki, C. Koike, Y. Aoyagi, and M. Takeuchi, “Vertical AlGaN deep ultraviolet light emitting diode emitting at 322 nm fabricated by the laser lift-off technique,” Appl. Phys. Lett. 89(26), 261114 (2006).
[Crossref]

2005 (3)

M. Khizar, Z. Y. Fan, K. H. Kim, J. Y. Lin, and H. X. Jiang, “Nitride deep-ultraviolet light-emitting diodes with microlens array,” Appl. Phys. Lett. 86(17), 173504 (2005).
[Crossref]

H. Hirayama, “Quaternary InAlGaN-based high-efficiency ultraviolet light-emitting diodes,” J. Appl. Phys. 97(9), 091101 (2005).
[Crossref]

D. W. Kim, H. Y. Lee, M. C. Yoo, and G. Y. Yeom, “Highly efficient vertical laser-liftoff GaN-based light-emitting diodes formed by optimization of the cathode structure,” Appl. Phys. Lett. 86(5), 052108 (2005).
[Crossref]

2004 (2)

T. Fujii, Y. Gao, R. Sharma, E. L. Hu, S. P. DenBaars, and S. Nakamura, “Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening,” Appl. Phys. Lett. 84(6), 855–857 (2004).
[Crossref]

T. Nishida, T. Makimoto, H. Saito, and T. Ban, “AlGaN-based ultraviolet light-emitting diodes grown on bulk AlN substrates,” Appl. Phys. Lett. 84(6), 1002–1003 (2004).
[Crossref]

2003 (1)

C. S. Chang, S. J. Chang, Y. K. Su, Y. C. Lin, Y. P. Hsu, S. C. Shei, S. C. Chen, C. H. Liu, and U. H. Liaw, “InGaN/GaN light emitting diodes with ITO p-contact layers prepared by RF sputteing,” Semicond. Sci. Technol. 18(4), L21–L23 (2003).
[Crossref]

2002 (1)

K. B. Nam, J. Li, M. L. Nakarmi, J. Y. Lin, and H. X. Jiang, “Achieving highly conductive AlGaN alloys with high Al contents,” Appl. Phys. Lett. 81(6), 1038–1040 (2002).
[Crossref]

1999 (2)

T. Margalith, O. Buchinsky, D. A. Cohen, A. C. Abare, M. Hansen, S. P. DenBaars, and L. A. Coldren, “Indium tin oxide contacts to gallium nitride optoelectronic devices,” Appl. Phys. Lett. 74(26), 3930–3932 (1999).
[Crossref]

S. K. Saha, R. S. Howell, and M. K. Hatalis, “Reaction Mechanisms in Aluminum-Indium Tin Oxide Ohmic Contact Metallization with Co and Ni Barrier Layers for Active-Matrix-Display Applications,” J. Electrochem. Soc. 146(8), 3134–3138 (1999).
[Crossref]

Abare, A. C.

T. Margalith, O. Buchinsky, D. A. Cohen, A. C. Abare, M. Hansen, S. P. DenBaars, and L. A. Coldren, “Indium tin oxide contacts to gallium nitride optoelectronic devices,” Appl. Phys. Lett. 74(26), 3930–3932 (1999).
[Crossref]

Adivarahan, V.

M. Lachab, F. Asif, B. Zhang, I. Ahmad, A. Heidari, Q. Fareed, V. Adivarahan, and A. Khan, “Enhancement of light extraction efficiency in sub-300 nm nitride thin-film flip-chip light-emitting diodes,” Solid-State Electron. 89, 156–160 (2013).
[Crossref]

V. Adivarahan, A. Heidari, B. Zhang, Q. Fareed, M. Islam, S. Hwang, K. Balakirshnan, and A. Khan, “Vertical Injection Thin Film Deep Ultraviolet Light Emitting Diodes with AlGaN Multiple-Quantum Wells Active Region,” Appl. Phys. Express 2(9), 092102 (2009).
[Crossref]

Ahmad, I.

M. Lachab, F. Asif, B. Zhang, I. Ahmad, A. Heidari, Q. Fareed, V. Adivarahan, and A. Khan, “Enhancement of light extraction efficiency in sub-300 nm nitride thin-film flip-chip light-emitting diodes,” Solid-State Electron. 89, 156–160 (2013).
[Crossref]

Akasaki, I.

K. Takehara, K. Takeda, S. Ito, H. Aoshima, M. Iwaya, T. Takeuchi, S. Kamiyama, I. Akasaki, and H. Amano, “Indium–Tin Oxide/Al reflective electrodes for ultraviolet light-emitting diodes,” Jpn. J. Appl. Phys. 51(4R), 042101 (2012).
[Crossref]

K. Ban, J.-i. Yamamoto, K. Takeda, K. Ide, M. Iwaya, T. Takeuchi, S. Kamiyama, I. Akasaki, and H. Amano, “Internal quantum efficiency of whole-composition-range AlGaN multi quantum wells,” Appl. Phys. Express 4(5), 052101 (2011).
[Crossref]

Alaskar, Y.

D. Priante, R. T. Elafandy, A. Prabaswara, B. Janjua, C. Zhao, M. S. Alias, M. Tangi, Y. Alaskar, A. M. Albadri, A. Y. Alyamani, T. K. Ng, and B. S. Ooi, “Diode junction temperature in ultraviolet AlGaN quantum-disks-in-nanowires,” J. Appl. Phys. 124(1), 015702 (2018).
[Crossref]

Albadri, A. M.

D. Priante, R. T. Elafandy, A. Prabaswara, B. Janjua, C. Zhao, M. S. Alias, M. Tangi, Y. Alaskar, A. M. Albadri, A. Y. Alyamani, T. K. Ng, and B. S. Ooi, “Diode junction temperature in ultraviolet AlGaN quantum-disks-in-nanowires,” J. Appl. Phys. 124(1), 015702 (2018).
[Crossref]

Alias, M. S.

D. Priante, R. T. Elafandy, A. Prabaswara, B. Janjua, C. Zhao, M. S. Alias, M. Tangi, Y. Alaskar, A. M. Albadri, A. Y. Alyamani, T. K. Ng, and B. S. Ooi, “Diode junction temperature in ultraviolet AlGaN quantum-disks-in-nanowires,” J. Appl. Phys. 124(1), 015702 (2018).
[Crossref]

Alyamani, A. Y.

D. Priante, R. T. Elafandy, A. Prabaswara, B. Janjua, C. Zhao, M. S. Alias, M. Tangi, Y. Alaskar, A. M. Albadri, A. Y. Alyamani, T. K. Ng, and B. S. Ooi, “Diode junction temperature in ultraviolet AlGaN quantum-disks-in-nanowires,” J. Appl. Phys. 124(1), 015702 (2018).
[Crossref]

Amano, H.

K. Takehara, K. Takeda, S. Ito, H. Aoshima, M. Iwaya, T. Takeuchi, S. Kamiyama, I. Akasaki, and H. Amano, “Indium–Tin Oxide/Al reflective electrodes for ultraviolet light-emitting diodes,” Jpn. J. Appl. Phys. 51(4R), 042101 (2012).
[Crossref]

K. Ban, J.-i. Yamamoto, K. Takeda, K. Ide, M. Iwaya, T. Takeuchi, S. Kamiyama, I. Akasaki, and H. Amano, “Internal quantum efficiency of whole-composition-range AlGaN multi quantum wells,” Appl. Phys. Express 4(5), 052101 (2011).
[Crossref]

Aoshima, H.

K. Takehara, K. Takeda, S. Ito, H. Aoshima, M. Iwaya, T. Takeuchi, S. Kamiyama, I. Akasaki, and H. Amano, “Indium–Tin Oxide/Al reflective electrodes for ultraviolet light-emitting diodes,” Jpn. J. Appl. Phys. 51(4R), 042101 (2012).
[Crossref]

Aoyagi, Y.

M. Takeuchi, T. Maegawa, H. Shimizu, S. Ooishi, T. Ohtsuka, and Y. Aoyagi, “AlN/AlGaN short-period superlattice sacrificial layers in laser lift-off for vertical-type AlGaN-based deep ultraviolet light emitting diodes,” Appl. Phys. Lett. 94(6), 061117 (2009).
[Crossref]

K. Kawasaki, C. Koike, Y. Aoyagi, and M. Takeuchi, “Vertical AlGaN deep ultraviolet light emitting diode emitting at 322 nm fabricated by the laser lift-off technique,” Appl. Phys. Lett. 89(26), 261114 (2006).
[Crossref]

Asif, F.

M. Lachab, F. Asif, B. Zhang, I. Ahmad, A. Heidari, Q. Fareed, V. Adivarahan, and A. Khan, “Enhancement of light extraction efficiency in sub-300 nm nitride thin-film flip-chip light-emitting diodes,” Solid-State Electron. 89, 156–160 (2013).
[Crossref]

Balakirshnan, K.

V. Adivarahan, A. Heidari, B. Zhang, Q. Fareed, M. Islam, S. Hwang, K. Balakirshnan, and A. Khan, “Vertical Injection Thin Film Deep Ultraviolet Light Emitting Diodes with AlGaN Multiple-Quantum Wells Active Region,” Appl. Phys. Express 2(9), 092102 (2009).
[Crossref]

Balakrishnan, K.

A. Khan, K. Balakrishnan, and T. Katona, “Ultraviolet light-emitting diodes based on group three nitrides,” Nat. Photonics 2(2), 77–84 (2008).
[Crossref]

Ban, K.

K. Ban, J.-i. Yamamoto, K. Takeda, K. Ide, M. Iwaya, T. Takeuchi, S. Kamiyama, I. Akasaki, and H. Amano, “Internal quantum efficiency of whole-composition-range AlGaN multi quantum wells,” Appl. Phys. Express 4(5), 052101 (2011).
[Crossref]

Ban, T.

T. Nishida, T. Makimoto, H. Saito, and T. Ban, “AlGaN-based ultraviolet light-emitting diodes grown on bulk AlN substrates,” Appl. Phys. Lett. 84(6), 1002–1003 (2004).
[Crossref]

Bryan, I.

Z. Bryan, I. Bryan, J. Xie, S. Mita, Z. Sitar, and R. Collazo, “High internal quantum efficiency in AlGaN multiple quantum wells grown on bulk AlN substrates,” Appl. Phys. Lett. 106(14), 142107 (2015).
[Crossref]

Bryan, Z.

Z. Bryan, I. Bryan, J. Xie, S. Mita, Z. Sitar, and R. Collazo, “High internal quantum efficiency in AlGaN multiple quantum wells grown on bulk AlN substrates,” Appl. Phys. Lett. 106(14), 142107 (2015).
[Crossref]

Buchinsky, O.

T. Margalith, O. Buchinsky, D. A. Cohen, A. C. Abare, M. Hansen, S. P. DenBaars, and L. A. Coldren, “Indium tin oxide contacts to gallium nitride optoelectronic devices,” Appl. Phys. Lett. 74(26), 3930–3932 (1999).
[Crossref]

Cao, W.

C. Lu, L. Wang, J. Lu, R. Li, L. Liu, D. Li, N. Liu, L. Li, W. Cao, W. Yang, W. Chen, W. Du, C. T. Lee, and X. Hu, “Investigation of the electroluminescence spectrum shift of InGaN/GaN multiple quantum well light-emitting diodes under direct and pulsed currents,” J. Appl. Phys. 113(1), 013102 (2013).
[Crossref]

Chang, C. S.

C. S. Chang, S. J. Chang, Y. K. Su, Y. C. Lin, Y. P. Hsu, S. C. Shei, S. C. Chen, C. H. Liu, and U. H. Liaw, “InGaN/GaN light emitting diodes with ITO p-contact layers prepared by RF sputteing,” Semicond. Sci. Technol. 18(4), L21–L23 (2003).
[Crossref]

Chang, S. J.

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T. Fujii, Y. Gao, R. Sharma, E. L. Hu, S. P. DenBaars, and S. Nakamura, “Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening,” Appl. Phys. Lett. 84(6), 855–857 (2004).
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[Crossref]

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N. Maeda, J. Yum, M. Jo, and H. Hirayama, “Enhancing the light-extraction efficiency of AlGaN deep-ultraviolet light-emitting diodes using highly reflective Ni/Mg and Rh as p-type electrodes,” Jpn. J. Appl. Phys. 57(4S), 04FH08 (2018).
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L. Zhou, J. E. Epler, M. R. Krames, W. Goets, M. Gherasimova, Z. Ren, J. Han, M. Kneissl, and N. M. Johnson, “Vertical injection thin-film AlGaN/AlGaN multiple-quantum-well deep ultraviolet light-emitting diodes,” Appl. Phys. Lett. 89(24), 241113 (2006).
[Crossref]

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H. Hirayama, N. Maeda, S. Fujikawa, S. Toyoda, and N. Kamata, “Recent progress and future prospects of AlGaN-based high-efficiency deep-ultraviolet light-emitting diodes,” Jpn. J. Appl. Phys. 53(10), 100209 (2014).
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M. Lachab, F. Asif, B. Zhang, I. Ahmad, A. Heidari, Q. Fareed, V. Adivarahan, and A. Khan, “Enhancement of light extraction efficiency in sub-300 nm nitride thin-film flip-chip light-emitting diodes,” Solid-State Electron. 89, 156–160 (2013).
[Crossref]

V. Adivarahan, A. Heidari, B. Zhang, Q. Fareed, M. Islam, S. Hwang, K. Balakirshnan, and A. Khan, “Vertical Injection Thin Film Deep Ultraviolet Light Emitting Diodes with AlGaN Multiple-Quantum Wells Active Region,” Appl. Phys. Express 2(9), 092102 (2009).
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A. Khan, K. Balakrishnan, and T. Katona, “Ultraviolet light-emitting diodes based on group three nitrides,” Nat. Photonics 2(2), 77–84 (2008).
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M. Khizar, Z. Y. Fan, K. H. Kim, J. Y. Lin, and H. X. Jiang, “Nitride deep-ultraviolet light-emitting diodes with microlens array,” Appl. Phys. Lett. 86(17), 173504 (2005).
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D. W. Kim, H. Y. Lee, M. C. Yoo, and G. Y. Yeom, “Highly efficient vertical laser-liftoff GaN-based light-emitting diodes formed by optimization of the cathode structure,” Appl. Phys. Lett. 86(5), 052108 (2005).
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M. Khizar, Z. Y. Fan, K. H. Kim, J. Y. Lin, and H. X. Jiang, “Nitride deep-ultraviolet light-emitting diodes with microlens array,” Appl. Phys. Lett. 86(17), 173504 (2005).
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M. Kneissl, T. Kolbe, C. Chua, V. Kueller, N. Lobo, J. Stellmach, A. Knauer, H. Rodriguez, S. Einfeldt, and Z. Yang, “Advances in group III-nitride-based deep UV light-emitting diode technology,” Semicond. Sci. Technol. 26(1), 014036 (2011).
[Crossref]

L. Zhou, J. E. Epler, M. R. Krames, W. Goets, M. Gherasimova, Z. Ren, J. Han, M. Kneissl, and N. M. Johnson, “Vertical injection thin-film AlGaN/AlGaN multiple-quantum-well deep ultraviolet light-emitting diodes,” Appl. Phys. Lett. 89(24), 241113 (2006).
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K. Kawasaki, C. Koike, Y. Aoyagi, and M. Takeuchi, “Vertical AlGaN deep ultraviolet light emitting diode emitting at 322 nm fabricated by the laser lift-off technique,” Appl. Phys. Lett. 89(26), 261114 (2006).
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M. Kneissl, T. Kolbe, C. Chua, V. Kueller, N. Lobo, J. Stellmach, A. Knauer, H. Rodriguez, S. Einfeldt, and Z. Yang, “Advances in group III-nitride-based deep UV light-emitting diode technology,” Semicond. Sci. Technol. 26(1), 014036 (2011).
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L. Zhou, J. E. Epler, M. R. Krames, W. Goets, M. Gherasimova, Z. Ren, J. Han, M. Kneissl, and N. M. Johnson, “Vertical injection thin-film AlGaN/AlGaN multiple-quantum-well deep ultraviolet light-emitting diodes,” Appl. Phys. Lett. 89(24), 241113 (2006).
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M. Lachab, F. Asif, B. Zhang, I. Ahmad, A. Heidari, Q. Fareed, V. Adivarahan, and A. Khan, “Enhancement of light extraction efficiency in sub-300 nm nitride thin-film flip-chip light-emitting diodes,” Solid-State Electron. 89, 156–160 (2013).
[Crossref]

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C. Lu, L. Wang, J. Lu, R. Li, L. Liu, D. Li, N. Liu, L. Li, W. Cao, W. Yang, W. Chen, W. Du, C. T. Lee, and X. Hu, “Investigation of the electroluminescence spectrum shift of InGaN/GaN multiple quantum well light-emitting diodes under direct and pulsed currents,” J. Appl. Phys. 113(1), 013102 (2013).
[Crossref]

Lee, H. Y.

D. W. Kim, H. Y. Lee, M. C. Yoo, and G. Y. Yeom, “Highly efficient vertical laser-liftoff GaN-based light-emitting diodes formed by optimization of the cathode structure,” Appl. Phys. Lett. 86(5), 052108 (2005).
[Crossref]

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C. Lu, L. Wang, J. Lu, R. Li, L. Liu, D. Li, N. Liu, L. Li, W. Cao, W. Yang, W. Chen, W. Du, C. T. Lee, and X. Hu, “Investigation of the electroluminescence spectrum shift of InGaN/GaN multiple quantum well light-emitting diodes under direct and pulsed currents,” J. Appl. Phys. 113(1), 013102 (2013).
[Crossref]

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Y. Guo, Y. Zhang, J. Yan, H. Xie, L. Liu, X. Chen, M. Hou, Z. Qin, J. Wang, and J. Li, “Light extraction enhancement of AlGaN-based ultraviolet light-emitting diodes by substrate sidewall roughening,” Appl. Phys. Lett. 111(1), 011102 (2017).
[Crossref]

P. Dong, J. Yan, J. Wang, Y. Zhang, C. Geng, T. Wei, P. Cong, Y. Zhang, J. Zeng, Y. Tian, L. Sung, Q. Yan, J. Li, S. Fan, and Z. Qin, “282-nm AlGaN-based deep ultraviolet light-emitting diodes with improved performance on nano-patterned sapphire substrates,” Appl. Phys. Lett. 102(24), 241113 (2013).
[Crossref]

K. B. Nam, J. Li, M. L. Nakarmi, J. Y. Lin, and H. X. Jiang, “Achieving highly conductive AlGaN alloys with high Al contents,” Appl. Phys. Lett. 81(6), 1038–1040 (2002).
[Crossref]

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C. Lu, L. Wang, J. Lu, R. Li, L. Liu, D. Li, N. Liu, L. Li, W. Cao, W. Yang, W. Chen, W. Du, C. T. Lee, and X. Hu, “Investigation of the electroluminescence spectrum shift of InGaN/GaN multiple quantum well light-emitting diodes under direct and pulsed currents,” J. Appl. Phys. 113(1), 013102 (2013).
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P. Dong, J. Yan, J. Wang, Y. Zhang, C. Geng, T. Wei, P. Cong, Y. Zhang, J. Zeng, Y. Tian, L. Sung, Q. Yan, J. Li, S. Fan, and Z. Qin, “282-nm AlGaN-based deep ultraviolet light-emitting diodes with improved performance on nano-patterned sapphire substrates,” Appl. Phys. Lett. 102(24), 241113 (2013).
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P. Dong, J. Yan, J. Wang, Y. Zhang, C. Geng, T. Wei, P. Cong, Y. Zhang, J. Zeng, Y. Tian, L. Sung, Q. Yan, J. Li, S. Fan, and Z. Qin, “282-nm AlGaN-based deep ultraviolet light-emitting diodes with improved performance on nano-patterned sapphire substrates,” Appl. Phys. Lett. 102(24), 241113 (2013).
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Y. Guo, Y. Zhang, J. Yan, H. Xie, L. Liu, X. Chen, M. Hou, Z. Qin, J. Wang, and J. Li, “Light extraction enhancement of AlGaN-based ultraviolet light-emitting diodes by substrate sidewall roughening,” Appl. Phys. Lett. 111(1), 011102 (2017).
[Crossref]

P. Dong, J. Yan, J. Wang, Y. Zhang, C. Geng, T. Wei, P. Cong, Y. Zhang, J. Zeng, Y. Tian, L. Sung, Q. Yan, J. Li, S. Fan, and Z. Qin, “282-nm AlGaN-based deep ultraviolet light-emitting diodes with improved performance on nano-patterned sapphire substrates,” Appl. Phys. Lett. 102(24), 241113 (2013).
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P. Dong, J. Yan, J. Wang, Y. Zhang, C. Geng, T. Wei, P. Cong, Y. Zhang, J. Zeng, Y. Tian, L. Sung, Q. Yan, J. Li, S. Fan, and Z. Qin, “282-nm AlGaN-based deep ultraviolet light-emitting diodes with improved performance on nano-patterned sapphire substrates,” Appl. Phys. Lett. 102(24), 241113 (2013).
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D. Priante, R. T. Elafandy, A. Prabaswara, B. Janjua, C. Zhao, M. S. Alias, M. Tangi, Y. Alaskar, A. M. Albadri, A. Y. Alyamani, T. K. Ng, and B. S. Ooi, “Diode junction temperature in ultraviolet AlGaN quantum-disks-in-nanowires,” J. Appl. Phys. 124(1), 015702 (2018).
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[Crossref]

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Figures (6)

Fig. 1.
Fig. 1. Schematic drawing of (a) cross-sectional and (b) tile-view of Ga-face n-contact type vertical LED structure.
Fig. 2.
Fig. 2. Scanning electron micrograph of the roughened N-face n-AlGaN surface etched by an alkali solution. (a) The tilt-view image and (b) plane-view after the passivation deposition on the extractor surface with a diameter of approximately 0.5 µm.
Fig. 3.
Fig. 3. Relative reflectivities of ITO/Al, Ni/Au, Ni(2 nm)/Al(150 nm), and Rh(150 nm) layers deposited on sapphire substrate. Reflectivity was calibrated based on aluminum 92%.
Fig. 4.
Fig. 4. Current-voltage (I-V) characteristics of 1 × 1mm2 vertical chip fabricated with Ni/Au and ITO/Al p-type electrodes.
Fig. 5.
Fig. 5. (a) I-L and (b) I-EQE characteristics of UV-C vertical LEDs according to p-type mirror electrode and surface roughness. (1 × 1mm2 vertical chip)
Fig. 6.
Fig. 6. Characteristics of (a) light output power-current-voltage (L-I-V), (b) peak wavelength-current, and (c) junction temperature-current at ambient temperature of 60°C for the 1.3 × 1.3mm2 vertical chip and flip chip of UV-C LED.

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