Ag/Ni/Ag Multilayer Reflector for GaN-Based Vertical Light-Emitting Diode

Yum, Woong Sun; Jeon, Joon Woo; Sung, Jun Suk; Jin, Sung‐Ho; Seong, Tae Yeon

doi:10.7567/jjap.52.052101

Cited by 8 publications

(6 citation statements)

References 29 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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“…Temperature-dependent optical properties show that these films can preserve their high reflectivity at high temperatures. Record-high reflectivity, large mechanical hardness, structural and thermal stability, high melting temperatures, and CMOS compatibility make HfN and ZrN attractive alternative materials for solar mirrors in photovoltaics, 57 heatassisted magnetic recordings, 58 high-brightness light-emitting diode (LED) devices, 59 and passive daytime radiative cooling applications. 60…”

Section: ■ Conclusionmentioning

confidence: 99%

Refractory Plasmonic Hafnium Nitride and Zirconium Nitride Thin Films as Alternatives to Silver for Solar Mirror Applications

Das

Biswas

Maurya

et al. 2022

ACS Appl. Mater. Interfaces

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Harnessing solar energy by employing concentrated solar power (CSP) systems requires materials with high electrical conductivity and optical reflectivity. Silver, with its excellent optical reflectance, is traditionally used as a reflective layer in solar mirrors for CSP technologies. However, silver is soft and expensive, quickly tarnishes, and requires a protective layer of glass for practical applications. Moreover, supply-side constraints and high-temperature instability of silver have led to the search for alternative materials that exhibit high solar and infrared reflectance. Transition metal nitrides, such as titanium nitride, have emerged as alternative plasmonic materials to gold starting from a spectral range of ∼500 nm. However, to achieve high solar reflection (∼320–2500 nm), materials with epsilon-near-zero starting from the near-ultraviolet (UV) spectral region are required. Here, we show the development of refractory epitaxial hafnium nitride (HfN) and zirconium nitride (ZrN) thin films as excellent mirrors with a solar reflectivity of ∼90.3% and an infrared reflectivity of ∼95%. Low-loss and high-quality epsilon-near-zero resonance at near-UV (∼340–380 nm) spectral regions are achieved in HfN and ZrN by carefully controlling the stoichiometry, leading to a sharp increase in the reflection edge that is on par with silver. Temperature-dependent reflectivity and dielectric constants are further measured to demonstrate their high-temperature suitability. The development of refractory epitaxial HfN and ZrN thin films with high solar and infrared reflectance makes them excellent alternative plasmonic materials to silver and would pave their applications in CSP, daytime radiative cooling, and others.

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“…On the other hand, Ag suffers thermal instability, such as agglomeration at temperatures above 300 °C . For this reason, many studies have been performed to overcome the agglomeration of Ag that is related to thermal degradation, such as Ag‐based alloys , interlayers , and inserted layers . For example, Ag‐based alloys, such as AgAl and AgCu alloys, effectively improved the thermal stability of Ag films.…”

Section: Introductionmentioning

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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Ag/Ni/Ag Multilayer Reflector for GaN-Based Vertical Light-Emitting Diode

Cited by 8 publications

References 29 publications

Identifying Key Factors towards Highly Reflective Silver Coatings

Identifying Key Factors towards Highly Reflective Silver Coatings

Refractory Plasmonic Hafnium Nitride and Zirconium Nitride Thin Films as Alternatives to Silver for Solar Mirror Applications

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

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