나노크기 표면 요철을 이용한 GaN LED의 광추출효율 향상

정재우; 김사라; 정준호; 정종율; Jae-Woo Jung; Sarah Kim; Jun Ho Jeong; Jong-Ryul Jeong

Korean Journal of Materials Research, Vol.22, No.11, 636-642, November, 2012

DOI10.3740/MRSK.2012.22.11.636 Export Citation

나노크기 표면 요철을 이용한 GaN LED의 광추출효율 향상

Enhancement of Light Extraction Efficiency of GaN Light Emitting Diodes Using Nanoscale Surface Corrugation

정재우¹, 김사라², 정준호 ², 정종율^{1, 3, †}

¹충남대학교 재료공학과
²한국기계연구원 나노공정장비연구실
³충남대학교 녹색에너지기술전문대학원

Jae-Woo Jung¹, Sarah Kim², Jun Ho Jeong², and Jong-Ryul Jeong^{1, 3, †}

¹Department of Materials Science and Engineering, Chungnam National University, Daejeon 305-764, Korea
²Nanomechanical System Research Center, Korea Institute of Machinery and Materials (KIMM), Daejeon 305-343, Korea
³Graduate School of Green Energy Technology, Chungnam National University, Daejeon 305-764, Korea

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In this study, we have investigated highly efficient nanoscale surface corrugated light emitting diodes (LEDs) for the enhancement of light extraction efficiency (LEE) of nitride semiconductor LEDs. Nanoscale indium tin oxide (ITO) surface corrugations are fabricated by using the conformal nanoimprint technique; it was possible to observe an enhancement of LEE for the ITO surface corrugated LEDs. By incorporating this novel method, we determined that the total output power of the surface corrugated LEDs were enhanced by 45.6% for patterned sapphire substrate LEDs and by 41.9% for flat c-plane substrate LEDs. The enhancement of LEE through nanoscale surface corrugations was studied using 3-dimensional Finite Different Time Domain (FDTD) calculation. From the FDTD calculations, we were able to separate the light extraction from the top and bottom sides of device. This process revealed that light extraction from the top and bottom sides of a device strongly depends on the substrate and the surface corrugation. We found that enhanced LEE could be understood through the mechanism of enhanced light transmission due to refractive index matching and the increase of light scattering from the corrugated surface. LEE calculations for the encapsulated LEDs devices also revealed that low LEE enhancement is expected after encapsulation due to the reduction of the refractive index contrast.

Keywords:light emitting diodes;surface corrugation;nanoimprint;light extraction efficiency;Finite-Different Time- Domain(FDTD)

[References]

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Krames MR, Ochiai-Holcomb M, Hofler GE, Carter-Coman C, Chen EI, Tan IH, Grillot P, Gardner NF, Chui HC, Huang JW, Stockman SA, Kish FA, Craford MG, Tan TS, Kocot CP, Hueschen M, Posselt J, Loh B, Sasser G, Collins D, Appl. Phys. Lett., 75, 2365 (1999)
Schnitzer I, Yablonovitch E, Caneau C, Gmitter TJ, Scherer A, Appl. Phys. Lett., 63, 2174 (1993)
Tadatomo K, Okagawa H, Ohuchi Y, Tsunekawa T, Imada Y, Kato M, Taguchi T, Jpn. J. Appl. Phys., 40, L583 (2001)
Kim JY, Kwon MK, Lee KS, Park SJ, Kim SH, Lee KD, Appl. Phys. Lett., 91, 181109 (2007)
Zhong J, Chen H, Saraf G, Lu Y, Choi CK, Song JJ, Mackie DM, Shen H, Appl. Phys. Lett., 90, 203515 (2007)
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FDTD solutions on the Web. Retrieved Oct. 8, 2012 from http://www.lumerical.com/ (2012)
Kim S, Kim SM, Park HH, Choi DG, Jung JW, Jeong JH, Jeong JR, Opt. Express, 20, A713 (2012)
Park HH, Choi DG, Zhang X, Jeon S, Park SJ, Lee SW, Kim S, Kim KD, Choi JH, Lee J, Yun DK, Lee KJ, Park HH, Hill RH, Jeong JH, J. Mater. Chem., 20, 1921 (2010)
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[Related Articles]

[1] Schubert EF, Kim JK, Science, 308, 1274 (2005)

[2] Krames MR, Shchekin OB, Mueller-Mach R, Mueller GO, Zhou L, Harbers G, Craford MG, J. Display Technol., 3(2), 160 (2007)

[3] Schnitzer I, Yablonovitch E, Caneau C, Gmitter TJ, Appl. Phys. Lett., 62(2), 131 (1993)

[4] Schubert EF, Light Emitting Diodes, 2nd ed., p. 86, Cambridge University Press, Cambridge, England (2006). (2006)

[5] Sheng X, Broderic LZ, Hu J, Yang L, Eshed A, Fitzgerald EA, Michel J, Kimerling LC, Opt. Express, 19, A701 (2011)

[6] Krames MR, Ochiai-Holcomb M, Hofler GE, Carter-Coman C, Chen EI, Tan IH, Grillot P, Gardner NF, Chui HC, Huang JW, Stockman SA, Kish FA, Craford MG, Tan TS, Kocot CP, Hueschen M, Posselt J, Loh B, Sasser G, Collins D, Appl. Phys. Lett., 75, 2365 (1999)

[7] Schnitzer I, Yablonovitch E, Caneau C, Gmitter TJ, Scherer A, Appl. Phys. Lett., 63, 2174 (1993)

[8] Tadatomo K, Okagawa H, Ohuchi Y, Tsunekawa T, Imada Y, Kato M, Taguchi T, Jpn. J. Appl. Phys., 40, L583 (2001)

[9] Kim JY, Kwon MK, Lee KS, Park SJ, Kim SH, Lee KD, Appl. Phys. Lett., 91, 181109 (2007)

[10] Zhong J, Chen H, Saraf G, Lu Y, Choi CK, Song JJ, Mackie DM, Shen H, Appl. Phys. Lett., 90, 203515 (2007)

[11] Baek KS, Jo MS, Lee YG, Sadasivam KG, Song YH, Kim SH, Kim JK, Jeon SR, Lee JK, Korean J. Mater. Res., 21(5), 273 (2011)

[12] FDTD solutions on the Web. Retrieved Oct. 8, 2012 from http://www.lumerical.com/ (2012)

[13] Kim S, Kim SM, Park HH, Choi DG, Jung JW, Jeong JH, Jeong JR, Opt. Express, 20, A713 (2012)

[14] Park HH, Choi DG, Zhang X, Jeon S, Park SJ, Lee SW, Kim S, Kim KD, Choi JH, Lee J, Yun DK, Lee KJ, Park HH, Hill RH, Jeong JH, J. Mater. Chem., 20, 1921 (2010)

[15] Park HH, Zhang X, Lee SW, Kim KD, Choi DG, Choi JH, Lee J, Lee ES, Park HH, Hill RH, Jeong JH, J. Mater. Chem., 21, 657 (2011)

[16] Ambacher O, Brunner D, Dimitrov R, Stutzmann M, Sohmer A, Scholz F, Jpn. J. Appl. Phys., 37, 745 (1998)