Enhanced optical output of GaN-based near-ultraviolet light-emitting diodes using an ultra-thin air cavity nanopatterned sapphire substrate

Gai, Zheng; Chang, Le; Shao, Hua; Chu, Chunshuang; Fan, Chao; Zhang, Yandi; Zhang, Yonghui; Zhang, Zihui

doi:10.1039/d2ce00150k

Cited by 2 publications

(1 citation statement)

References 38 publications

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“…The LEE has been increased by two fold compared to the flat sapphire substrate. [107] The secondary optics are equally important to collimate the high divergence output light from LED primary optics. The free-form optics in terms of design freedom of the lens curvature provides better control of light irradiation and high-quality LEDs [108][109][110][111][112][113].…”

Section: Noticeable Improvementmentioning

confidence: 99%

A Review of Critical Issues in High-Speed Vat Photopolymerization

et al. 2023

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Vat photopolymerization (VPP) is an effective additive manufacturing (AM) process known for its high dimensional accuracy and excellent surface finish. It employs vector scanning and mask projection techniques to cure photopolymer resin at a specific wavelength. Among the mask projection methods, digital light processing (DLP) and liquid crystal display (LCD) VPP have gained significant popularity in various industries. To upgrade DLP and LCC VPP into a high-speed process, increasing both the printing speed and projection area in terms of the volumetric print rate is crucial. However, challenges arise, such as the high separation force between the cured part and the interface and a longer resin refilling time. Additionally, the divergence of the light-emitting diode (LED) makes controlling the irradiance homogeneity of large-sized LCD panels difficult, while low transmission rates of near ultraviolet (NUV) impact the processing time of LCD VPP. Furthermore, limitations in light intensity and fixed pixel ratios of digital micromirror devices (DMDs) constrain the increase in the projection area of DLP VPP. This paper identifies these critical issues and provides detailed reviews of available solutions, aiming to guide future research towards developing a more productive and cost-effective high-speed VPP in terms of the high volumetric print rate.

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Section: Noticeable Improvementmentioning

confidence: 99%

A Review of Critical Issues in High-Speed Vat Photopolymerization

et al. 2023

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Suppressing optical crosstalk for GaN/InGaN based flip-chip micro light-emitting diodes by using an air-cavity patterned sapphire substrate as a light filter

jia¹,

zhang²,

Gai³

et al. 2023

Opt. Express

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In this work, by using three-dimensional finite-difference time-domain (3D FDTD) method, the effect of conventional nano-patterned sapphire substrate (NPSS) on the optical crosstalk and the light extraction efficiency (LEE) for InGaN/GaN-based flip-chip micro light-emitting diodes (µ-LEDs) are systematically studied. We find that the conventional NPSS is not suitable for µ-LEDs. It is because the inclined mesa sidewall for µ-LEDs possesses a good scattering effect for µ-LEDs, but the introduced conventional NPSS causes part of the light be off escape cone between sapphire and air and become the guided light. To suppress the guided light and improve the optical crosstalk, a thick air layer between the n-GaN layer and the sapphire substrate can be used as a light filter to prevent the guided light from propagating into the sapphire. However, in reality, it is challenging to make the aforementioned air layer from point of fabrication view. Therefore, we propose the air-cavity patterned sapphire substrate (AC-PSS) as the light filter. Our results show that the crosstalk ratio can be decreased to the value even lower than 10%. The LEE can also be enhanced simultaneously due to combination effects of the filtering effect of the AC-PSS and the scattering effect of the inclined mesa sidewall.

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Enhanced optical output of GaN-based near-ultraviolet light-emitting diodes using an ultra-thin air cavity nanopatterned sapphire substrate

Abstract: In this work, an ultra-thin air-cavity nanopatterned sapphire substrate (UTAC-NPSS) is fabricated by using a combined nanotechnology of nanosphere lens lithography technology, atomic layer deposition (ALD) and partial exposure lithography...

Cited by 2 publications

References 38 publications

A Review of Critical Issues in High-Speed Vat Photopolymerization

A Review of Critical Issues in High-Speed Vat Photopolymerization

Suppressing optical crosstalk for GaN/InGaN based flip-chip micro light-emitting diodes by using an air-cavity patterned sapphire substrate as a light filter

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