나노크기 표면 요철을 이용한 GaN LED의 광추출효율 향상 = Enhancement of Light Extraction Efficiency of GaN Light Emitting Diodes Using Nanoscale Surface Corrugation

다국어 초록 (Multilingual 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.

참고문헌 (Reference)

1 E. F. Schubert, 308 : 1274-, 2005

2 O. Ambacher, 37 : 745-, 1998

3 I. Schnitzer, 62 (62): 131-, 1993

4 M. R. Krames, 3 (3): 160-, 2007

5 H. -H. Park, 21 : 657-, 2011

6 H. -H. Park, 20 : 1921-, 2010

7 X. Sheng, 19 : A701-, 2011

8 M. R. Krames, 75 : 2365-, 1999

9 I. Schnitzer, 63 : 2174-, 1993

10 K. Tadatomo, 40 : L583-, 2001

11 J. -Y. Kim, 91 : 181109-, 2007

12 J. Zhong, 90 : 203515-, 2007

13 S. Kim, 20 : A713-, 2012

14 백광선, "나노 구조의 패턴을 갖는 n-type GaN 기판을 이용한 380 nm UV-LED의 광 추출 효율 개선" 한국재료학회 21 (21): 273-276, 2011

15 E. F. Schubert, "Light Emitting Diodes, 2nd ed" Cambridge University Press 86-, 2006

16 "FDTD solutions on the Web"