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Energy Express

Energy Express

  • Editor: Christian Seassal
  • Vol. 22, Iss. S3 — May. 5, 2014
  • pp: A723–A734

Wafer-scale surface roughening for enhanced light extraction of high power AlGaInP-based light-emitting diodes

Hyeong-Ho Park, Xin Zhang, Yunae Cho, Dong-Wook Kim, Joondong Kim, Keun Woo Lee, Jehyuk Choi, Hee Kwan Lee, Sang Hyun Jung, Eun Jin Her, Chang Hwan Kim, A-Young Moon, Chan-Soo Shin, Hyun-Beom Shin, Ho Kun Sung, Kyung Ho Park, Hyung-Ho Park, Hi-Jung Kim, and Ho Kwan Kang  »View Author Affiliations

Optics Express, Vol. 22, Issue S3, pp. A723-A734 (2014)

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A new approach to surface roughening was established and optimized in this paper for enhancing the light extraction of high power AlGaInP-based LEDs, by combining ultraviolet (UV) assisted imprinting with dry etching techniques. In this approach, hexagonal arrays of cone-shaped etch pits are fabricated on the surface of LEDs, forming gradient effective-refractive-index that can mitigate the emission loss due to total internal reflection and therefore increase the light extraction efficiency. For comparison, wafer-scale FLAT-LEDs without any surface roughening, WET-LEDs with surface roughened by wet etching, and DRY-LEDs with surface roughened by varying the dry etching time of the AlGaInP layer, were fabricated and characterized. The average output power for wafer-scale FLAT-LEDs, WET-LEDs, and DRY3-LEDs (optimal) at 350 mA was found to be 102, 140, and 172 mW, respectively, and there was no noticeable electrical degradation with the WET-LEDs and DRY-LEDs. The light output was increased by 37.3% with wet etching, and 68.6% with dry etching surface roughening, respectively, without compromising the electrical performance of LEDs. A total number of 1600 LED chips were tested for each type of LEDs. The yield of chips with an optical output power of 120 mW and above was 0.3% (4 chips), 42.8% (684 chips), and 90.1% (1441 chips) for FLAT-LEDs, WET-LEDs, and DRY3-LEDs, respectively. The dry etching surface roughening approach developed here is potentially useful for the industrial mass production of wafer-scale high power LEDs.

© 2014 Optical Society of America

OCIS Codes
(230.3670) Optical devices : Light-emitting diodes
(220.4241) Optical design and fabrication : Nanostructure fabrication

ToC Category:
Light-Emitting Diodes

Original Manuscript: January 30, 2014
Revised Manuscript: March 13, 2014
Manuscript Accepted: March 13, 2014
Published: March 31, 2014

Hyeong-Ho Park, Xin Zhang, Yunae Cho, Dong-Wook Kim, Joondong Kim, Keun Woo Lee, Jehyuk Choi, Hee Kwan Lee, Sang Hyun Jung, Eun Jin Her, Chang Hwan Kim, A-Young Moon, Chan-Soo Shin, Hyun-Beom Shin, Ho Kun Sung, Kyung Ho Park, Hyung-Ho Park, Hi-Jung Kim, and Ho Kwan Kang, "Wafer-scale surface roughening for enhanced light extraction of high power AlGaInP-based light-emitting diodes," Opt. Express 22, A723-A734 (2014)

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