Pulsed laser deposition of ITO/AZO transparent contact layers for GaN LED applications

doi:10.1364/OE.19.016244

Pulsed laser deposition of ITO/AZO transparent contact layers for GaN LED applications

Sin Liang Ou, Dong Sing Wuu, Shu Ping Liu, Yu Chuan Fu, Shih Cheng Huang, and Ray Hua Horng »View Author Affiliations

Optics Express, Vol. 19, Issue 17, pp. 16244-16251 (2011)
http://dx.doi.org/10.1364/OE.19.016244

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Abstract

In this study, indium-tin oxide (ITO)/Al-doped zinc oxide (AZO) composite films were fabricated by pulsed laser deposition and used as transparent contact layers (TCLs) in GaN-based blue light emitting diodes (LEDs). The ITO/AZO TCLs were composed of the thin ITO (50 nm) films and AZO films with various thicknesses from 200 to 1000 nm. Conventional LED with ITO (200 nm) TCL prepared by E-beam evaporation was fabricated and characterized for comparison. From the transmittance spectra, the ITO/AZO films exhibited high transparency above 90% at wavelength of 465 nm. The sheet resistance of ITO/AZO TCL decreased as the AZO thickness increased, which could be attributed to the increase in a carrier concentration, leading to a decrease in the forward bias of LED. The LEDs with ITO/AZO composite TCLs showed better light extraction as compared to LED with ITO TCL in compliance with simulation. When an injection current of 20 mA was applied, the output power for LEDs fabricated with ITO/AZO TCLs had 45%, 63%, and 71% enhancement as compared with those fabricated using ITO (200 nm) TCL for the AZO thicknesses of 200, 460, and 1000 nm, respectively.

OCIS Codes
(230.3670) Optical devices : Light-emitting diodes
(250.0250) Optoelectronics : Optoelectronics

ToC Category:
Optical Devices

History
Original Manuscript: June 20, 2011
Revised Manuscript: July 29, 2011
Manuscript Accepted: July 29, 2011
Published: August 9, 2011

Citation
Sin Liang Ou, Dong Sing Wuu, Shu Ping Liu, Yu Chuan Fu, Shih Cheng Huang, and Ray Hua Horng, "Pulsed laser deposition of ITO/AZO transparent contact layers for GaN LED applications," Opt. Express 19, 16244-16251 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-17-16244

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References

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G. K. Reeves and H. B. Harrison, “Obtaining the specific contact resistance from transmission line model measurements,” IEEE Electron Device Lett. 3(5), 111–113 (1982). [CrossRef]
B. Z. Dong, G. J. Fang, J.-F. Wang, W.-J. Guan, and X.-Z. Zhao, “Effect of thickness on structural, electrical, and optical properties of ZnO:Al films deposited by pulsed laser deposition,” J. Appl. Phys. 101(3), 033713 (2007). [CrossRef]
J. K. Sheu, Y. S. Lu, M. L. Lee, W. C. Lai, C. H. Kuo, and C. J. Tun, “Enhanced efficiency of GaN-based light-emitting diodes with periodic textured Ga-doped ZnO transparent contact layer,” Appl. Phys. Lett. 90(26), 263511 (2007). [CrossRef]
J. K. Sheu, M. L. Lee, Y. S. Lu, and K. W. Shu, “Ga-doped ZnO transparent conductive oxide films applied to GaN-based light-emitting diodes for improving light extraction efficiency,” IEEE J. Quantum Electron. 44(12), 1211–1218 (2008). [CrossRef]

Appl. Phys. Lett.

S. Nakamura, T. Mukai, and M. Senoh, “Candela-class high-brightness InGaN/AlGaN double-heterostructure blue-light-emitting diodes,” Appl. Phys. Lett. 64(13), 1687–1689 (1994). [CrossRef]
H. X. Jiang, S. X. Jin, J. Li, J. Shakya, and J. Y. Lin, “III-nitride blue microdisplays,” Appl. Phys. Lett. 78(9), 1303–1305 (2001). [CrossRef]
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. N. Oder, K. H. Kim, J. Y. Lin, and H. X. Jiang, “III-nitride blue and ultraviolet photonic crystal light emitting diodes,” Appl. Phys. Lett. 84(4), 466–468 (2004). [CrossRef]
C. C. Wang, H. Ku, C. C. Liu, K. K. Chong, C. I. Hung, Y. H. Wang, and M. P. Houng, “Enhancement of the light output performance for GaN-based light-emitting diodes by bottom pillar structure,” Appl. Phys. Lett. 91(12), 121109 (2007). [CrossRef]
T. Y. Park, Y. S. Choi, J. W. Kang, J. H. Jeong, S. J. Park, D. M. Jeon, J. W. Kim, and Y. C. Kim, “Enhanced optical power and low forward voltage of GaN-based light-emitting diodes with Ga-doped ZnO transparent conducting layer,” Appl. Phys. Lett. 96(5), 051124 (2010). [CrossRef]
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]
J. K. Sheu, Y. S. Lu, M. L. Lee, W. C. Lai, C. H. Kuo, and C. J. Tun, “Enhanced efficiency of GaN-based light-emitting diodes with periodic textured Ga-doped ZnO transparent contact layer,” Appl. Phys. Lett. 90(26), 263511 (2007). [CrossRef]

IEEE Electron Device Lett.

G. K. Reeves and H. B. Harrison, “Obtaining the specific contact resistance from transmission line model measurements,” IEEE Electron Device Lett. 3(5), 111–113 (1982). [CrossRef]

IEEE J. Quantum Electron.

J. K. Sheu, M. L. Lee, Y. S. Lu, and K. W. Shu, “Ga-doped ZnO transparent conductive oxide films applied to GaN-based light-emitting diodes for improving light extraction efficiency,” IEEE J. Quantum Electron. 44(12), 1211–1218 (2008). [CrossRef]

IEEE Photon. Technol. Lett.

S. M. Pan, R. C. Tu, Y. M. Fan, R. C. Yeh, and J. T. Hsu, “Enhanced output power of InGaN–GaN light-emitting diodes with high-transparency nickel-oxide–indium-tin-oxide ohmic contacts,” IEEE Photon. Technol. Lett. 15(5), 646–648 (2003). [CrossRef]
J. Y. Kim, M. K. Kwon, J. P. Kim, and S. J. Park, “Enhanced light extraction from triangular GaN-based light-emitting diodes,” IEEE Photon. Technol. Lett. 19(23), 1865–1867 (2007). [CrossRef]

J. Appl. Phys.

B. Z. Dong, G. J. Fang, J.-F. Wang, W.-J. Guan, and X.-Z. Zhao, “Effect of thickness on structural, electrical, and optical properties of ZnO:Al films deposited by pulsed laser deposition,” J. Appl. Phys. 101(3), 033713 (2007). [CrossRef]

J. Cryst. Growth

B. Y. Oh, M. C. Jeong, W. Lee, and J. M. Myoung, “Properties of transparent conductive ZnO:Al films prepared by co-sputtering,” J. Cryst. Growth 274(3-4), 453–457 (2005). [CrossRef]
S. M. Yang, S. K. Han, J. W. Lee, J. H. Kim, J. G. Kim, S. K. Hong, J. Y. Lee, J. H. Song, S. I. Hong, J. S. Park, and T. Yao, “Microstructural investigation of ZnO films grown on (1 1 1) Si substrates by plasma-assisted molecular beam epitaxy,” J. Cryst. Growth 312(9), 1557–1562 (2010). [CrossRef]

J. Electrochem. Soc.

N. Yoshii, A. Nakamura, S. Hosaka, and J. Temmyo, “Investigation of morphology and crystallinity of ZnO crystal formed by side-flow-type MOCVD,” J. Electrochem. Soc. 156(7), K117–K120 (2009). [CrossRef]
M. C. Lin, Y. J. Chang, M. J. Chen, and C. J. Chu, “Characteristics of Zr-doped ZnO thin films grown by atomic layer deposition,” J. Electrochem. Soc. 158(6), D395–D398 (2011). [CrossRef]
S. P. Liu, D. S. Wuu, S. L. Ou, Y. C. Fu, P. R. Lin, M. T. Hung, and R. H. Horng, “Highly ultraviolet-transparent ZnO:Al conducting layers by pulsed laser deposition,” J. Electrochem. Soc. 158(5), K127–K130 (2011). [CrossRef]

J. Vac. Sci. Technol. A

T. Minami, T. Miyata, and T. Yamamoto, “Stability of transparent conducting oxide films for use at high temperatures,” J. Vac. Sci. Technol. A 17(4), 1822–1826 (1999). [CrossRef]

Jpn. J. Appl. Phys.

K. M. Uang, S. J. Wang, S. L. Chen, C. K. Wu, S. C. Chang, T. M. Chen, and B. W. Liou, “High-power GaN-based light-emitting diodes with transparent indium zinc oxide films,” Jpn. J. Appl. Phys. 44(4BNo. 4B), 2516–2519 (2005). [CrossRef]

Opt. Express

Phys. Scr.

areA. Mahmood, N. Ahmed, Q. Raza, T. Muhammad Khan, M. Mehmood, M. M. Hassan, and N. Mahmood, “Effect of thermal annealing on the structural and optical properties of ZnO thin films deposited by the reactive e-beam evaporation technique,” Phys. Scr. 82(6), 065801 (2010). [CrossRef]

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