Morphological stability of Ag reflector for high-power GaN-based vertical light-emitting diode by addition of Ni layer

Choi, Young Yun; Seong, Tae Yeon

doi:10.1016/j.spmi.2014.06.007

Cited by 8 publications

(11 citation statements)

References 31 publications

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“…Improving the light extraction efficiency is vital for the development of HB LEDs. One of the methods is to reduce the light scattering by depositing a highly reflective silver (Ag) thin film on the lead frame surface [3][4][5][6][7][8]. The Ag layer also serves the purpose of enhancing the solderability and heat dissipation of the lead frame.…”

Section: Introductionmentioning

confidence: 99%

Identifying Key Factors towards Highly Reflective Silver Coatings

Zheng

Wong²,

et al. 2017

Advances in Materials Science and Engineering

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This paper attempts to identify key factor(s) for highly reflective silver (Ag) coatings. Investigation was made over the crystal orientation and surface roughness, using several types of surfaces, including electroplated Ag polycrystal films, physical vapour deposited polycrystal Ag films, and single crystal Ag foils with different crystal orientations. In each type of the surfaces, surface roughness was varied so that, for different combinations of crystal orientation, roughness would elucidate the key factors towards highly reflective Ag coatings. It is found that surface roughness plays a critical role in determining the reflectance, while the crystal orientation has negligible effect. The mean reflectance and one-way ANOVA analysis indicate that the single crystal Ag foils with three orientations performed statistically the same in the same roughness group at significance level = 0.05. Moreover, correlation between the surface reflectance and surface roughness has been proposed for the benefit of coating design. Refection data obtained from the polycrystalline silver samples are used to verify the accuracy of the proposed correlations. It was observed that the development surface area ratio, , is a better roughness indicator in predicting the reflectance of polycrystalline silver films than the arithmetic average roughness, .

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Section: Introductionmentioning

confidence: 99%

Identifying Key Factors towards Highly Reflective Silver Coatings

Zheng

Wong²,

et al. 2017

Advances in Materials Science and Engineering

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“…The Ag grain size was increased by EBI. In addition, the diffusion from small Ag grains to large Ag grains decreased due to increased Ag grains by EBI .…”

Section: Resultsmentioning

confidence: 99%

Improvement of thermal stability of Ag-based reflector in GaN-based flip chip LEDs by electron-beam irradiation

Lee

Cha

et al. 2017

Phys. Status Solidi A

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We proposed the effects of electron‐beam irradiation (EBI) on the Ag reflector for GaN‐based light‐emitting diodes (LEDs). To evaluate the thermal stability of Ag, we carried out a thermal aging test. The Ag with EBI showed a high reflectance of 97.9% at a 450 nm wavelength and higher thermal stability than the Ag reflector without EBI. Scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and X‐ray diffraction (XRD) were used to examine the surface and texture evolution of the Ag reflector before and after thermal aging at 300 °C for 120 min. SEM and EBSD showed that unlike the agglomeration occurred in the Ag reflector without EBI, the Ag reflector with EBI only showed an increase in grain size after thermal aging at 300 °C for 120 min. XRD data demonstrated the Ag reflector to have a higher <111>‐peak intensity due to EBI. On the other hand, after thermal aging at 300 °C for 120 min, the Ag reflector with EBI becomes less <111>‐peak than the Ag reflector without EBI. The difference in the surface and texture between the Ag reflectors with/without EBI is closely related to the changes in grain size and surface energy by thermal aging.

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“…The agglomeration usually causes a light scattering phenomenon and decreased conductivity with respect to the initial smooth layer, thus decreasing the specular reflection and conductivity [6][7][8][9][10]. In the past decade, thermal stability or thermal degradation (i.e., agglomeration) of Ag films on GaN-related semiconductors for LEDs have been extensively investigated in many studies [11][12][13][14][15][16][17][18][19][20]. One solution for improving the thermal stability of Ag films was proposed by adopting capping layers like NiZn alloy [11], SnO 2 [12], Zn [13], and IZO [15] on Ag films, or using interlayers like Ni [14] and Ir [15] layers beneath the Ag films, to retard the Ag agglomeration process at high temperature.…”

Section: Introductionmentioning

confidence: 99%

“…One solution for improving the thermal stability of Ag films was proposed by adopting capping layers like NiZn alloy [11], SnO 2 [12], Zn [13], and IZO [15] on Ag films, or using interlayers like Ni [14] and Ir [15] layers beneath the Ag films, to retard the Ag agglomeration process at high temperature. Another solution was forming Ag alloy films by adding several percent of Al [16],…”

Section: Introductionmentioning

confidence: 99%

Thermal Stability and Sulfidizing Resistance of High Reflective Multilayered Sn/Ag3Sn and Sn/Ag Films Electrodeposited on Cu Alloy Sheets

Kure‐Chu

Ogasawara

et al. 2016

Electrochimica Acta

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We reported multilayered Sn/Ag 3 Sn and Sn/Ag films with Ag thickness of 20-300 nm that electroplated on a reflowed Sn layer on Cu alloy sheets as promising coating materials for LED lead-frames. The morphology, surface roughness, crystalline structure, and reflectance of multilayered Sn/Ag-based films are more dependent on plating baths than on Ag thickness. The Sn/Ag 3 Sn film obtained from a cyanide Ag bath exhibited high specular reflectivity of 65-70% (480 nm), whereas the Sn/Ag films from a cyanide-free bath showed a high total reflectivity of 94% similar to commercial Ag films. The reflectance of both the multilayered Sn/Ag 3 Sn and Sn/Ag films almost unchanged even after heating at 373 K for 120 h, in comparison with the apparent drop for a commercial Ag film. Moreover, the multilayered Sn/Ag 3 Sn films, both the as-deposited and the annealed specimens, remained the reflectivity even after immersing in a

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Morphological stability of Ag reflector for high-power GaN-based vertical light-emitting diode by addition of Ni layer

Cited by 8 publications

References 31 publications

Identifying Key Factors towards Highly Reflective Silver Coatings

Identifying Key Factors towards Highly Reflective Silver Coatings

Improvement of thermal stability of Ag-based reflector in GaN-based flip chip LEDs by electron-beam irradiation

Thermal Stability and Sulfidizing Resistance of High Reflective Multilayered Sn/Ag3Sn and Sn/Ag Films Electrodeposited on Cu Alloy Sheets

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