Influence of ITO-Electrode Deposition Method on the Electro-optical Characteristics of Blue LEDs

ITO 전극 형성 방법이 청색 발광 다이오드의 전기 광학적 특성에 미치는 영향

  • Published : 2007.11.25

Abstract

We have investigated the electro-optical characteristics and reliability of LEDs with the Indium-Tin-Oxide (ITO) electrodes formed by different deposition methods: electron beam evaporation, sputtering, and hybrid method of electron beam evaporation and subsequent sputtering. The deposition method of the ITO electrode has significant influence on the electro-optical characteristics and reliability of LEDs. The LEDs with the ITO electrodes formed by sputtering and electron beam evaporation have problems caused by sputtering damage and increased electrical resistance, respectively, and the problems have been solved by the hybrid method.

ITO(Indium Tin Oxide) 전극 형성방법은 ITO 박막 자체의 전기 광학적 특성 뿐 아니라 ITO를 전극으로 하는 청색 발광 다이오드(파장 469nm)의 전기 광학적 특성 및 신뢰성에도 큰 영향을 미침을 확인하였다. 세 가지 ITO 전극 형성 방법 즉 electron beam evaporation법과 sputtering법, 그리고 electron beam evaporation법으로 먼저 증착한 뒤에 sputtering법으로 증착한 hybrid법 등을 사용하여 청색 발광 다이오드를 제작한 다음에 ITO 박막의 특성과 aging에 따른 발광 다이오드의 전기 광학적 특성 변화를 고찰하였다. 그 결과, ITO 전극을 sputtering 또는 electron beam evaporation 방법으로 형성한 발광 다이오드는 각각 sputtering damage의 문제와 전기저항이 증가하는 문제점을 안고 있음을 발견하였다. 그리고 이 문제점들을 hybrid 방법으로 해결하였다.

Keywords

References

  1. A. C. Arias, L. S Roman, T. Kugler, R. Toniolo, M. S. Meruvia, I. A. Hummelgen, 'The use of oxide thin films as a transparent electrode in PPV based light emitting diodes,' Thin Solid Films, vol. 371, pp.201-206, August 2000 https://doi.org/10.1016/S0040-6090(00)00967-6
  2. F. Zhu, K. Zhang, B. L. Low, S. F. Lim, S. J. Chua, 'Morphological and electrical properties of indium ti oxide films prepared at a low processing temperature for flexible organic light-emitting devices,' Materials Science and Engineering B, vol. 85, pp.114-117, August 2001 https://doi.org/10.1016/S0921-5107(01)00541-4
  3. D. Vautrey, M. B. Khalifa, M. P. Besland, J. Tardy, C. Sandu, M. G. Blanchin, J. A. Roger, 'Electrical and optical characteristics of indium tin oxide thin films deposited by cathodic sputtering for top emitting organic electroluminescent devices,' Materials Science and Engineering C, vol. 21, pp.265-271, September 2002 https://doi.org/10.1016/S0928-4931(02)00078-4
  4. D. C. Paine, T. Whitson, D. Janiac, R. Beresford, C. O. Yang, 'A study of low temperature crystallization of amorphous thin film indium-tin-oxide,' Journal of Applied Physics, vol. 85, no. 12, pp.8445-8450, June 1999 https://doi.org/10.1063/1.370695
  5. L. G. Mar, P. Y. Timbrell, and R. N. Lamb, 'An XPS study of zinc oxide thin film growth on copper using zinc acetate as a precursor,' Thin Solid Films, vol. 223, pp.341-347, February 1993 https://doi.org/10.1016/0040-6090(93)90542-W
  6. T. Ishida, H. Kobayashi, and Y. Nakato, 'Structure and properties of electron-beam -evaporated indium tin oxide films as studied by x-ray photoelectron spectroscopy and work -function measurements,' Journal of Applied Physics, vol. 73, no. 9, pp.4344-4350, May 1993 https://doi.org/10.1063/1.352818
  7. M. Higuchi, S. Uekusa, R. Nakano, K. Yokogawa, 'Micrograin structure influence on electrical characteristics of sputtered indium tin oxide films,' Journal of Applied Physics, vol. 74, no. 11, pp.6710-6713, December 1993 https://doi.org/10.1063/1.355093
  8. S. J. Rosner, E. C. Carr, M. J. Ludowise, G. Girolami, and H. I. Erikson, 'Correlation of cathodoluminescence inhomogeneity with microstructural defects in epitaxial GaN Grown by metalorganic chemical-vapor deposition,' Applied Physics Letters, vol. 70, no. 4, pp.420-422, January 1997 https://doi.org/10.1063/1.118322
  9. T. Hino, S. Tomiya, T. Miyajima, K. Yanashima, S. Hashimoto, and M. Ikeda, 'Characterization of Threading Dislocations in GaN Epitaxial Layers,' Applied Physics Letters, vol. 76, no. 23, pp. 3421 -3423, June 2000 https://doi.org/10.1063/1.126666
  10. P. Kozodoy, J. P. Ibbetson, H. Marchand, P. T. Fini, S. Keller, J. S. Speck, S. P. DenBaars, and U. K. Mishra, 'Electrical Characterization of GaN p-n Junctions with and without Threading Dislocations,' Applied Physics Letters, vol. 73, no. 7, pp.975-977, August 1998 https://doi.org/10.1063/1.122057
  11. J. W. P. Hsu, M. J. Manfra, D. V. Lang, S. Richter, S. N. G. Chu, A. M. Sergent, R. N. Kleiman, L. N. Pfeiffer, and R. J. Molnar, 'Inhomogeneous Spatial Distribution of Reverse Bias Leakage in GaN Schottky Diodes,' Applied Physics Letters, vol. 78, no. 12, pp.1685-1687, March 2001 https://doi.org/10.1063/1.1356450
  12. X. A. Cao, E. B. Stokes, P. M. Sandvik, S. F. LeBoeuf, J. Kretchmer, and D. Walker, 'Diffusion and Tunneling Currents in GaN/ InGaN Multiple Quantum Well Light-Emitting Diodes,' IEEE. Electron Device Letters, vol. 23, no. 9, pp.535-537, September 2002 https://doi.org/10.1109/LED.2002.802601