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, Ho Kwan Kang

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


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 coneshaped 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 waferscale 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.

Original languageEnglish
Pages (from-to)A723-A734
JournalOptics Express
Issue numberSUPPL. 3
StatePublished - 2014


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