Korean Journal of Materials Research (한국재료학회지)

Materials Research Society of Korea (한국재료학회)
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Enhancement of Light Extraction Efficiency of GaN Light Emitting Diodes Using Nanoscale Surface Corrugation

나노크기 표면 요철을 이용한 GaN LED의 광추출효율 향상

  • Jung, Jae-Woo (Department of Materials Science and Engineering, Chungnam National University) ;
  • Kim, Sarah (Nanomechanical System Research Center, Korea Institute of Machinery and Materials (KIMM)) ;
  • Jeong, Jun Ho (Nanomechanical System Research Center, Korea Institute of Machinery and Materials (KIMM)) ;
  • Jeong, Jong-Ryul (Department of Materials Science and Engineering, Chungnam National University)
  • 정재우 (충남대학교 재료공학과) ;
  • 김사라 (한국기계연구원 나노공정장비연구실) ;
  • 정준호 (한국기계연구원 나노공정장비연구실) ;
  • 정종율 (충남대학교 재료공학과)
  • Received : 2012.10.08
  • Accepted : 2012.11.08
  • Published : 2012.11.27
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Abstract

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.

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References

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