摘要(英) |
Light emitting diodes (LEDs) have various advantages such as small size, long life and good reliability. However, the light intensity distribution of native planar LED chips performed a Lambertian light pattern in spatial distribution. It caused the light intensity decay with viewing angle by cosine law. When LED emitting far-field pattern in the Lambertian formation, it became a weakly directional and non-uniform light source. In this thesis, we modulated the light pattern of LED chip, by the e-beam lithography and the dry etching processes integrated with LED chip process. Under this process integration, the 1-D sub-micron grating was fabricated on the chip surface to achieve the modulation of LEDs chip light pattern.
The light extraction enhancement was increased by the interaction between the emitting photon and the 1-D grating structure and the light pattern was also modulated. Five different periods of 1-D grating were designed (0.3 μm, 0.5 μm, 0.75 μm, 1.0 μm and 2.0 μm), and the angle-resolved measurements were completed under two luminescence mechanisms: the photoluminescence (PL) and the electroluminescence (EL).The results showed that the size of grating period affected the light patterns transition. In PL measurement, the grating period with 0.5μm, enhanced the light intensity at the observing angle of ±25°; the grating period with 2.0 μm, performed a light intensity in uniform between the observing angle of ±60°. The results of EL measurement were similar to that of PL. Furthermore, the effects of stimulated emission and spontaneous carrier recombination light pattern were evaluated by the FDTD analysis. The simulation results combined with different luminescence cases and the optics phenomenon resulted from the 1-D grating such as the scatter and the diffraction were used to discuss the relationship between the size of 1-D grating period, the far-field light patterns.
|
參考文獻 |
[1] H. Amano, M. kito, K.Hiramatsu and I. Akasaki, Jpn. J. Appl. Phys. 28, L2112 (1989).
[2] S. Nakamura, Jpn. J. Appl. Phys. 30,L1705 (1991).
[3] S. Nakamura, M. Senoh and T. Mukai, Jpn. J. Appl. Phys. 30, L1708 (1991).
[4] M. R. Krames, G. E. Höfler, E. I. Chen, I. H. Tan, P. Grillot, N. F. Gardner, H. C. Chui, J. W. Huang, S. A. Stockman, F. A. Kish, and M. G. Craford, “High powertruncated inverted pyramid AlxGa12x.0.5In0.5P/GaP light-emitting diodes exhibiting >50% external quantum efficiency,” Applied physics letters, Vol. 75, pp. 2365, 1999.
[5] J. Y. Kim, M. K. Kwon, J. P. Kim, and S. J. Park, “ Enhanced Light Extraction From Triangular GaN-Based Light-Emitting Diodes,” IEEE Phot. Tech. Lett., Vol. 19, NO.23, 2007.
[6] Chul Huh, Kug-Seung Lee, Eun-Jeong Kang, and Seong-Ju Park, “Improved light-output and electrical performance of InGaN-based light-emitting diode by microroughening of the p-GaN surface,” Journal of Applied Physics, Vol. 93, No. 11, pp.9383, 2003.
[7 ] H. Kim, J. Cho, J. W. Lee, S. Yoon, H. Kim, C. Sone, and Y. Park,
“Enhanced light extraction of GaN-based light-emitting diodes by using textured n-type GaN layers, ” Applied physics letters, Vol. 90, pp. 161110, 2007.
[8] K. Bao, X. N. Kang, B. Zhang, T. Dai, C. Xiong, H. Ji, G. Y. Zhang, and Y. Chen, “Improvement of Light Extraction From Patterned Polymer Encapsulated GaN-Based Flip-Chip Light-Emitting Diodes by Imprinting,” IEEE , Vol. 19, pp. 20, 2007.
[9] 林佳裕,壓印技術至做表面微結構應用於圖樣化藍寶石基板發光二極體之研究,中央大學,2009
[10] E. Fred Schubert,「Light – Emitting Diodes」,CAMBRIDGE,2006
[11] 史光國,「半導體發光二極體及固體照明」,全華科技圖書股份有限公司印行,2006
[12] Dong-Ho Kim, Chi-O Cho, Yeong-Geun Roh, Heonsu Jeon, and Yoon Soo Park, “Enhanced light extraction from GaN-based light emitting diodes with holographically generated two-dimensional photonic crystal patterns.” Appl. Phys. Lett. 87, 203508 (2005).
[13] J. J. Wierer , M. R. Kramesa , J. E. Eplera , N. F. Gardnera , J. R.
Wendtb , M. M. Sigalasc , S. R. J. Brueckd , D. Lid , and M. Shagame “III-Nitride LEDs with photonic crystal structures ” SPIE Vol. 5739( 2005 )
[14] Aurélien David, Tetsuo Fujii, Rajat Sharma, Kelly McGroddy, Shuji Nakamura, Steven P. DenBaars, Evelyn L. Hu, and Claude Weisbuch, “Photonic-crystal GaN light-emitting diodes with tailored guided modes distribution” Applied physics letters 88, 061124 (2006).
[15] Aurélien David, Henri Benisty, and Claude Weisbuch,“Optimization of Light-Diffracting Photonic-Crystals for High Extraction Efficiency LEDs” Journal of Display Technology, vol. 3, no. 2, 2007.
|