Enhancing the Light-Extraction Efficiency of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes by Optimizing the Diameter and Tilt of the Aluminum Sidewall

Pai, Yung Min; Lin, Chih Hao; Lee, Chun Fu; Lin, Chun Peng; Chen, Cheng-Huan; Kuo, Hao‐Chung; Ye, Zhi Ting

doi:10.3390/cryst8110420

Cited by 15 publications

(6 citation statements)

References 35 publications

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“…Therefore, to improve the reliability of UVB-LEDs, the mainstream design for packaging has involved flipping the LED chip bonded onto the AlN-based LFs and using an attached quartz glass as a hermetic cover. This kind of packaging structure for DUV-LEDs comes, however, with higher materials costs, severely decreased light extraction, and limited optical performance [17][18][19][20]. Some DUV-transparent encapsulation materials have been proposed to ameliorate these drawbacks such as sol−gel methyl siloxane hybrid material, fluorine resins, and liquid packaging structure.…”

Section: Introductionmentioning

confidence: 99%

Epoxy Molding Compound Lead Frames With Silicone Resin for Encapsulating AlGaN-Based UVB Light-Emitting Diodes

Liu

Huang

Lai³

et al. 2021

IEEE Access

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In this paper we report epoxy molding compound lead frames (EMC-LFs) with encapsulated silicone as a simple and inexpensive packaging for AlGaN-based ultraviolet-B (UVB) light-emitting diodes (LEDs) displaying high light extracting efficiencies (LEE) and long operation lifetimes. The convex surfaces and beveled shapes obtained after curing the encapsulated silicone surrounding the UVB-LED chips significantly enhanced the light output power (LOP). With silicone present inside the EMC-LFs having bonding cavity diameters of 1.7 and 1.45 mm, the LOPs of the UVB-LEDs improved by 26 and 42%, respectively; reliability tests performed over a period of 1000 h revealed, however, that the LOPs decreased to 70 and 71%, respectively, of their initial values, but no cracks appeared in the silicone during such longterm operation. Thus, the stability of silicone-encapsulating EMC-LFs for UVB-LEDs was acceptable. When compared with AlN-based direct plating copper ceramic lead frames (AlN-DPC-LFs), our proposed packaging structure and method have the potential to lower the manufacturing cost of UVB-LEDs.INDEX TERMS AlGaN, AlGaN-based ultraviolet-B LEDs, Packaging, Light output power.

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Section: Introductionmentioning

confidence: 99%

Epoxy Molding Compound Lead Frames With Silicone Resin for Encapsulating AlGaN-Based UVB Light-Emitting Diodes

Liu

Huang

Lai³

et al. 2021

IEEE Access

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“…of National Chiao Tung University proposed an aluminum‐based sidewall reflector to enhance the LEE of AlGaN‐based deep UV LED, as a result the output power increases by 18.38%. [ 116 ]…”

Section: Recent Advances In Packaging Technologiesmentioning

confidence: 99%

Recent Advances in Packaging Technologies of AlGaN‐Based Deep Ultraviolet Light‐Emitting Diodes

Liang

Sun

2022

Adv Materials Technologies

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AlGaN‐based deep ultraviolet light‐emitting diodes (UV LEDs) have gained rapidly growing attention due to their wide applications in water purification, air disinfection, and sensing as well as optical communication. Moreover, deep UV radiation has been verified as one of effective way to inactivate COVID‐19. However, although numerous efforts have been made in deep UV LED chips, the reported highest external quantum efficiency (EQE) of them is 20.3%, which is far lower than that of visible LEDs. The EQE of commercial packaged AlGaN‐based deep UV LEDs is usually lower than 5%, which will cause serious reliability problems as well. Therefore, it is very urgent to improve EQE and reliability of the devices from packaging level. In this review, a systematical summarization about the packaging technologies of AlGaN‐based deep UV LEDs has been analyzed and future prospects have been made as well. Firstly, this work provides a brief overview of the devices and analyzes why the packaging level reduces EQE and reliability in theory. Then, systematically reviews the recent advances in packaging technologies and deep UV micro‐LEDs. Finally, conclusions and outlooks are given as well. This review is of great significance for promoting the development of the packaging technologies for AlGaN‐based deep UV LEDs.

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“…LEE is affected by the chip layout, holder sidewall geometry, encapsulation material inside the cavity and the lens. Many approaches, such as the use of a flexible fluoropolymer film covering the top surfaces and sidewalls to improve the transverse electric and transverse magnetic mode [22], strategies such as a special silicone oil-based liquid packaging structure [23] to optimize the geometry and increased the reflectivity of the sidewalls [24][25][26] and novel three-dimensional quartz [27] have been used to improve the extraction efficiency. However, to the best of our knowledge, there are no studies that take advantage of the synergy of the highly reflective vertically shaped holder sidewall and the highly reflective holder substrate to elevate the LEE of DUV-LEDs.…”

Section: Introductionmentioning

confidence: 99%

Improved light extraction efficiency of AlGaN DUV light emitting diodes using Al/MgF₂-based highly reflective film

Li,

Huang,

Yang

et al. 2024

Semicond. Sci. Technol.

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AlGaN DUV light emitting diodes (DUV-LEDs) (275 nm emission) are safe, eco-friendly and smart alternatives for inactivating viruses and bacteria. However, DUV-LEDs suffer from the main bottleneck of low external quantum efficiencies, which are strongly associated with the low light extraction efficiency caused by the strong optical polarisation of Al-rich AlGaN. Optical simulation results show that the luminous intensity of DUV-LEDs was increased by 10% owing to the synergistic effect of the sidewalls and substrates. The optical power of DUV-LEDs was increased to 16.8%, the far-field pattern was expanded to 130 degrees and the emission intensity was more focus on the central region, proving that the highly reflective sidewalls and substrates could re-direct the sideways-travelling photons for extraction. Moreover, we also investigated the reflective mechanism of Al/MgF2 layers. Optimise refractive index distribution of Al/MgF2 layers could change the electric field intensity to improve the reflectivity. Meanwhile, the temperature of the sample after coating were significantly reduced by 7.33%. Thermal radiation benefits and the high stability of bonding interface are the main reasons to reduce the temperature of DUVLEDs after Al/MgF2 coating. The present strategy is proposed from the view of the chip fabrication, which is cost-effective, able to be manufactured at a large scale.

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Enhancing the Light-Extraction Efficiency of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes by Optimizing the Diameter and Tilt of the Aluminum Sidewall

Cited by 15 publications

References 35 publications

Epoxy Molding Compound Lead Frames With Silicone Resin for Encapsulating AlGaN-Based UVB Light-Emitting Diodes

Epoxy Molding Compound Lead Frames With Silicone Resin for Encapsulating AlGaN-Based UVB Light-Emitting Diodes

Recent Advances in Packaging Technologies of AlGaN‐Based Deep Ultraviolet Light‐Emitting Diodes

Improved light extraction efficiency of AlGaN DUV light emitting diodes using Al/MgF₂-based highly reflective film

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Enhancing the Light-Extraction Efficiency of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes by Optimizing the Diameter and Tilt of the Aluminum Sidewall

Cited by 15 publications

References 35 publications

Epoxy Molding Compound Lead Frames With Silicone Resin for Encapsulating AlGaN-Based UVB Light-Emitting Diodes

Epoxy Molding Compound Lead Frames With Silicone Resin for Encapsulating AlGaN-Based UVB Light-Emitting Diodes

Recent Advances in Packaging Technologies of AlGaN‐Based Deep Ultraviolet Light‐Emitting Diodes

Improved light extraction efficiency of AlGaN DUV light emitting diodes using Al/MgF2-based highly reflective film

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Improved light extraction efficiency of AlGaN DUV light emitting diodes using Al/MgF₂-based highly reflective film