Journal of the Korean Institute of Electrical and Electronic Material Engineers (한국전기전자재료학회논문지)

The Korean Institute of Electrical and Electronic Material Engineers (한국전기전자재료학회)
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Chip Size-Dependent Light Extraction Efficiency for Blue Micro-LEDs

청색 마이크로 LED의 광 추출 효율에 미치는 칩 크기 의존성 연구

  • Park, Hyun Jung (Department of Printed Electronics Engineering, Sunchon National University) ;
  • Cha, Yu-Jung (Department of Printed Electronics Engineering, Sunchon National University) ;
  • Kwak, Joon Seop (Department of Printed Electronics Engineering, Sunchon National University)
  • 박현정 (순천대학교 인쇄전자공학과) ;
  • 차유정 (순천대학교 인쇄전자공학과) ;
  • 곽준섭 (순천대학교 인쇄전자공학과)
  • Received : 2018.09.20
  • Accepted : 2018.10.12
  • Published : 2019.01.01

Abstract

Micro-LEDs show lower efficiencies compared to general LEDs having large areas. Simulations were carried out using ray-tracing software to investigate the change in light extraction efficiency and light distribution according to chip-size of blue flip-chip micro-LEDs (FC ${\mu}-LEDs$). After fixing the height of the square FC ${\mu}-LED$ chip at $158{\mu}m$, the length of one side was varied, with dimensions of 2, 5, 10, 30, 50, 100, 300, and $500{\mu}m$. The highest light-extraction efficiency was obtained at $10{\mu}m$, beyond which the efficiency decreased as the chip-size increased. The chip size-dependence of the FC ${\mu}-LEDs$ both without the patterned sapphire substrate, as well as vertical FC ${\mu}-LEDs$, were analyzed.

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Fig. 1. Cross-sectional image of the FC μ-LEDs.

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Fig. 4. Far-field light intensity angular distribution for the FC Fig. 2. (a) Result of light extraction efficiency and (b) side/top ratio according to changing the length of one side of the FC μ-LEDs.

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Fig. 5. Image of the ray tracing according to changing thelength of one side of the FC μ-LEDs.

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Fig. 7. Far-field light intensity angular distribution for the nonPSS FC μ-LEDs.

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Fig. 9. Far-field light intensity angular distribution for the verticalFC μ-LEDs.

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Fig. 10. Light extraction efficiency of (a) total, (b) top, and (c) 4 sides area according to changing the length of one side of the LEDs.

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Fig. 2. (a) Result of light extraction efficiency and (b) side/top ratio according to changing the length of one side of the FC μ-LEDs.

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Fig. 6. (a) Result of light extraction efficiency and (b) side/top ratio according to changing the length of one side of the non PSS FC μ-LEDs.

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Fig. 8. (a) Result of light extraction efficiency and (b) side/top ratio according to changing the length of one side of the vertical FC μ-LEDs.

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Fig. 3. Image of the side irradiance according to changing the length of one side of the FC Fig. 2. (a) Result of light extraction efficiency and (b) side/top ratio according to changing the length of one side of the FC μ-LEDs.

Table 1. Height and refractive index of the each layer.

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Acknowledgement

Supported by : 한국연구재단

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