Nitride-Based LEDs With High-Reflectance and Wide-Angle Ag Mirror${+}$SiO$_{2}$/TiO$_{2}$ DBR Backside Reflector

Lin, Nan-Ming; Shei, Shih–Chang; Chang, Shoou‐Jinn

doi:10.1109/jlt.2011.2111416

Cited by 18 publications

(15 citation statements)

References 13 publications

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“…1(b). The thickness of each layer and its respective relative refractive index [5] can be found in Fig. 1(c).…”

Section: Methodsmentioning

confidence: 99%

“…For the verification of the current simulations, the simulated results for the light output as a function of BR reflectance (R BR ) for the naked monotonic blue color emitting LED chip, are compared with the available experimental data [5]. As shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

“…For those LEDs, various types of chip-level backside reflectors (BRs) with a reflectance as high as of 98 % have been developed for adding on their backside, with an aim of enhancing its light output. An enhancement of as high as of 50 % is reported [4][5][6]. Because of those results, the chip level BR is now often adopted as a part of mesa-LED chip structure.…”

Section: Introductionmentioning

confidence: 98%

“…Because of those results, the chip level BR is now often adopted as a part of mesa-LED chip structure. However, the reported enhancement measurements based on the naked chip [4,5] might not be relevant to practical applications: Firstly, an enhancement from a naked chip does not necessarily lead to an equivalent enhancement for a packaged LED emitter. This is because light output of the LED emitter is strongly influenced by packaging materials and process [7,8].…”

Section: Introductionmentioning

confidence: 99%

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Optical role of die attach adhesive for white LED emitters: light output enhancement without chip-level reflectors

Kim

Shih

You³

et al. 2015

J Sol State Light

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A thin optical reflector is often introduced to the backside of the standard mesa type light emitting diode (LED) chip with the aim to enhance its light output. However, most of the reported light output enhancements because of backside reflector (BR) introduction might not be relevant. This is because the reported measurement is often from a naked LED chip instead of a packaged LED emitter, and those based on the packaged emitters employing conventional silver based die attach adhesive (DAA). The actual role of BR, which is expected to be greatly influenced by the packaging materials and processes, is investigated for the monotonic blue color and white LED emitters using Monte-Carlo simulations. Contrary to prior reports, it is demonstrated for the first time that the role of BR can be diminished when the optically transparent DAA is used and other key packaging materials and processes are optimized, i.e., the light output for a packaged emitter with a BR-free chip can be as high as that of the packaged emitter using the same chip but with an added BR.

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“…1(b). The thickness of each layer and its respective relative refractive index [5] can be found in Fig. 1(c).…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Optical role of die attach adhesive for white LED emitters: light output enhancement without chip-level reflectors

Kim

Shih

You³

et al. 2015

J Sol State Light

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show abstract

“…Integration of a backside reflector (BR) has been found to hugely enhance the light extraction (up to 50%) [1]- [5]. However, the reported huge enhancement with a BR by Lin is mainly for naked LED chips without the practical packaging procedure and materials [2]. Firstly, the measurement methods cannot reflect the effect of packaging factors, including the packaging materials, such as the reflector cup and die attach adhesives (DAAs), and processing conditions.…”

Section: Introductionmentioning

confidence: 99%

Optical Interaction Between LED Backside Reflectors and Die Attach Adhesives

Shih¹,

Kim²,

You³

et al. 2016

IEEE Photon. Technol. Lett.

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Adding optical reflectors to the backside of GaN-based light-emitting diode (LED) chip has been adopted for enhancing the light output. The optical effectiveness of backside reflectors (BRs) in enhancing light output is investigated by studying the light output of packaged mid-power blue and white LED emitters based on BR-based and BR-free chips. It is found that the effectiveness is strongly dependent on the optical properties of die attach adhesive (DAA) materials. When epoxy-silver DAA is applied, the difference in light output between the gold BR-based and BR-free blue LED chips is about 9% points at 40% coverage. However, with optically clear or reflective DAAs, BR-free chips show higher light output than the gold BR-based chips. For the optically clear DAA with 40% coverage, a 20% point enhancement of the output power of blue LED chips is obtained by the high transmittance of the DAA and high reflectance of the silver plating on the leadframe. With the optically reflective DAA, the enhancement for blue LED chips is ∼22% points due to the high reflectance of the DAA. This letter suggests a cost-effective method for enhancing the light output of mid-power LED emitters based on relatively low-cost BR-free LED chips by using optically clear or reflective DAAs depending on the applications and with a low fillet coverage for both materials.

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Investigation of Ni/Ag contact to p‐GaN with an O₂ plasma treatment and its application to GaN‐based LEDs

Lin

Shei

Chang

2012

Physica Status Solidi (a)

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In this paper, the contact structure of Ni–Ag/p‐GaN with different O2 plasma treatment times for 1 and 5 min was utilized for investigation. From experimental results, the Ni–Ag contact to p‐GaN with different O2 plasma treatment for 1 and 5 min reveals Schottky behaviors. Based on the variation of the specific contact resistance with respect to temperature, the dominant transport mechanism of Ni–Ag/p‐GaN structure presented form thermionic emission to field emission as increasing time from 1 to 5 min. From the X‐ray photoelectron spectroscopy (XPS) results, the increase of the N vacancies and antisite defects (ON) would enhance the resistance of the treated p‐GaN underneath the contact, which would make the Ni–Ag/p‐GaN contact reveal Schottky behavior. With a 20 mA current injection, the operation voltage of light‐emitting diodes (LEDs) with Ni/Ag contact to p‐GaN through O2 plasma treatment 400 W–5 min was 3.13 V larger than the LEDs with Ni/Ag contact to p‐GaN through O2 plasma treatment 400 W–1 min. This is due to the larger specific contact resistance. The 3.13 V operation voltage is still good and acceptable. Furthermore, the largest output power among all devices can be achieved. Besides, the reliability is still good.

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Nitride-Based LEDs With High-Reflectance and Wide-Angle Ag Mirror${+}$SiO$_{2}$/TiO$_{2}$ DBR Backside Reflector

Cited by 18 publications

References 13 publications

Optical role of die attach adhesive for white LED emitters: light output enhancement without chip-level reflectors

Optical role of die attach adhesive for white LED emitters: light output enhancement without chip-level reflectors

Optical Interaction Between LED Backside Reflectors and Die Attach Adhesives

Investigation of Ni/Ag contact to p‐GaN with an O₂ plasma treatment and its application to GaN‐based LEDs

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Nitride-Based LEDs With High-Reflectance and Wide-Angle Ag Mirror${+}$SiO$_{2}$/TiO$_{2}$ DBR Backside Reflector

Cited by 18 publications

References 13 publications

Optical role of die attach adhesive for white LED emitters: light output enhancement without chip-level reflectors

Optical role of die attach adhesive for white LED emitters: light output enhancement without chip-level reflectors

Optical Interaction Between LED Backside Reflectors and Die Attach Adhesives

Investigation of Ni/Ag contact to p‐GaN with an O2 plasma treatment and its application to GaN‐based LEDs

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Product

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Investigation of Ni/Ag contact to p‐GaN with an O₂ plasma treatment and its application to GaN‐based LEDs