Light output enhancement of GaN-based flip-chip light-emitting diodes fabricated with SiO2/TiO2 distributed Bragg reflector coated on mesa sidewall

Baik, Kwang Hyeon; Min, Byungsul; Kim, J. Y.; Kim, H. K.; Sone, Cheolsoo; Park, Y.; Kim, H.

doi:10.1063/1.3478740

Cited by 11 publications

(4 citation statements)

References 27 publications

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“…Assuming that the output power from the side wall and back side is neglected, only about 4% of the light generated in the multiple quantum well (MQW) can escape into the surrounding space. [8] Various methods have been proposed to increase the extraction efficiency, such as surface patterning techniques, [9][10][11][12][13][14][15] inclined side-wall etching, [16,17] and patterned sapphire substrate (PSS). [18,19] Among these approaches, surface patterning is one of the most efficient methods to provide a large enhancement factor of the LEE, due to the increased scattering rate at the roughened surface.…”

Section: Introductionmentioning

confidence: 99%

Tuning a nano-pillar array for enhancing the photoluminescence extraction efficiency of GaN-based light-emitting diodes

Xia¹,

Zhu-Hong²,

Chen³

et al. 2013

Chinese Phys. B

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We demonstrate the fabrication of hexagonal nano-pillar arrays at the surface of GaN-based light-emitting diodes (LEDs) by nanosphere lithography. By varying the oxygen plasma etching time, we could tune the size and shape of the pillar. The nano-pillar has a truncated cone shape. The nano-pillar array serves as a gradual effective refractive index matcher, which reduces the reflection and increases light cone. It is found that the patterned surface absorbs more pumping light. To compare extraction efficiencies of LEDs, it is necessary to normalize the photoluminescence power spectrum with total absorption rate under fixed pumping power, then we could obtain the correct enhancement factor of the photoluminescence extraction efficiency and optimized structure. The highest enhancement factor of the extraction efficiency is 10.6.

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Section: Introductionmentioning

confidence: 99%

Tuning a nano-pillar array for enhancing the photoluminescence extraction efficiency of GaN-based light-emitting diodes

Xia¹,

Zhu-Hong²,

Chen³

et al. 2013

Chinese Phys. B

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“…2(a)). In the DBR, a quarterwave SiO 2 (n = 1.5) and TiO 2 (n = 2.5) were stacked in an alternating way over a specific period [18]. The DBR can be used in thin-film flip chip [19] or vertical slab GaN LEDs [3,5,10,12] where the sapphire substrate is removed by laser lift-off technique.…”

Section: Coherent Coupling With Bragg Mirrorsmentioning

confidence: 99%

Coherent vertical beaming using Bragg mirrors for high-efficiency GaN light-emitting diodes

Kim¹,

Park²

2013

Opt. Express

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We propose a dielectric Bragg mirror that utilizes coherent coupling with multiple quantum wells (MQWs) to significantly enhance light extraction from GaN light-emitting diode (LED). Full vectorial electromagnetic simulation showed that, under constructive interference conditions, the Bragg mirror consisting of two dielectric (SiO(2)/TiO(2)) stacks and a silver layer led to >30% enhancement in light extraction, as compared to a single silver mirror. Such significant enhancement by a pre-designed Bragg/metal mirror was ascribed to the vertically oriented radiation pattern and reduced plasmonic metal loss. In addition, the gap distance between the MQWs and a Bragg mirror at which the constructive interference takes place could be controlled by modulating the thickness of the first low-refractive-index layer. Moreover, a two-dimensional periodic pattern was incorporated into an upper GaN layer with the designed Bragg mirror and it was shown that a lattice constant of ~800 nm was optimal for light extraction. We believe that tailoring the radiation profile of light emitters by coherent coupling with designed high-reflectivity mirrors will be a promising route to overcome the efficiency limit of current semiconductor LED devices.

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“…Various reflectors, such as metallic reflectors [12,17,18], distributed Bragg reflectors (DBRs) [19][20][21][22], omnidirectional reflectors [23,24], and hybrid reflectors [25], have been proposed to attain high light extraction efficiency (LEE) and to further boost external quantum efficiency of FC LEDs. Owing to high reflectivity, metallic reflectors and DBRs are widely applied in FC mini-LEDs.…”

Section: Introductionmentioning

confidence: 99%

Strategically constructed high-reflectivity multiple-stack distributed Bragg reflectors for efficient GaN-based flip-chip mini-LEDs

Shi

Sun

Cui

et al. 2023

J. Phys. D: Appl. Phys.

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Full-angle distributed Bragg reflectors (DBRs) consisting of numerous sub-DBRs with discrete central wavelengths have been developed to enhance performance of GaN-based flip-chip mini light-emitting diodes (FC mini-LEDs). However, relatively low reflectivity of full-angle DBRs at large angle incidence restricts further enhancement in performance of FC mini-LEDs. Here, we introduce a reflectivity optimization strategy for constructing high-reflectivity multiple-stack DBRs by rationally engineering the number of sub-DBRs and adjusting central wavelength distribution of sub-DBRs. Based on the reflectivity optimization strategy, we devise a Ti3O5/SiO2 quintuple-stack DBR which is composed of five sub-DBRs. Our quintuple-stack DBR maintains a high reflectivity (>97.5%) over a wide range of incident angles of light. Notably, compared with the full-angle DBR, our quintuple-stack DBR exhibits higher reflectivity at large angle incidence and thinner multilayer thickness. Furthermore, we demonstrate two types of GaN-based blue FC mini-LEDs with indium-tin oxide (ITO)/quintuple-stack DBR and ITO/full-angle DBR p-type ohmic contacts. Benefiting from superior reflection performance, blue FC mini-LED with ITO/quintuple-stack DBR achieves an enhancement of ~5.8% in light output power at 10 mA, in comparison with blue FC mini-LED with ITO/full-angle DBR. Our work signifies an advancement towards high-reflectivity DBRs, which enables higher-performance FC mini-LEDs.

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Light output enhancement of GaN-based flip-chip light-emitting diodes fabricated with SiO2/TiO2 distributed Bragg reflector coated on mesa sidewall

Cited by 11 publications

References 27 publications

Tuning a nano-pillar array for enhancing the photoluminescence extraction efficiency of GaN-based light-emitting diodes

Tuning a nano-pillar array for enhancing the photoluminescence extraction efficiency of GaN-based light-emitting diodes

Coherent vertical beaming using Bragg mirrors for high-efficiency GaN light-emitting diodes

Strategically constructed high-reflectivity multiple-stack distributed Bragg reflectors for efficient GaN-based flip-chip mini-LEDs

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