On the metallic bonding of GaN-based vertical light-emitting diode

Khan, Mansoor A.; Trimby, Patrick; Liu, Hong Wei; Zheng, Rongkun

doi:10.1016/j.mssp.2017.02.025

Cited by 9 publications

(7 citation statements)

References 62 publications

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“…60 Moreover, contrary to HAGBs, special Σ3 TBs are considered to be poor pathways for electromigration voiding or mass transport. 38,60 Interestingly, OM also highlights the position of special TBs, and it can be observed that the width of twins (diagonal lines) at the Ag layer gets sharp while moving toward the Ag/GaN interface, that is, narrow twins are slightly toward the upper GaN layer (Figure 5b). The measured average twin spacing in the Ag film is found to be ∼10 nm.…”

Section: Resultsmentioning

confidence: 93%

“…In fact, special TBs with less interfacial energy have low electrical resistance and less mobility compared with HAGBs . Moreover, contrary to HAGBs, special Σ3 TBs are considered to be poor pathways for electromigration voiding or mass transport. , …”

Section: Experimental Results and Discussionmentioning

confidence: 99%

“…The process flow of fabricating VLEDs involved four steps: ,, (1) metal–organic chemical vapor deposition (MOCVD) of epitaxial layers grown on a sapphire substrate and deposition of a reflective mirror by electron-beam evaporation, diffusion barrier, adhesive, and bonding metal layers; (2) wafer bonding to the carrier substrate; (3) removal of the sapphire substrate by using laser lift-off technique; and (4) surface structuring on the LED die. The schematic cross section of the final VLED device is illustrated in Figure .…”

Section: Methodsmentioning

confidence: 99%

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Insights into the Silver Reflection Layer of a Vertical LED for Light Emission Optimization

Khan¹,

Chen²,

Qu³

et al. 2017

ACS Appl. Mater. Interfaces

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In this work, Ag as a highly reflective mirror layer of gallium nitride (GaN)-based blue vertical light-emitting diodes (VLEDs) has been systematically investigated by correlating scanning electron microscopy/energy dispersive X-ray spectroscopy/transmission Kikuchi diffraction/electron backscatter diffraction, aberration-corrected scanning transmission electron microscopy, and atomic force microscopy techniques. In the context of high-efficiency lighting, three critical aspects have been scrutinized on the nanoscale: (1) chemical diffusion, (2) grain morphology, and (3) surface topography of the Ag layer. We found that nanoscale inhomogeneous distribution of In in InGaN/GaN quantum wells (QWs), interfacial diffusion (In/Ga out-diffusion into the Ag layer and diffusion of Ag into p-GaN and QWs), and Ag agglomeration deteriorate the light reflectivity, which account for the decreased luminous efficiency in VLEDs. Meanwhile, the surface morphology and topographical analyses revealed the nanomorphology of the Ag layer, where a nanograin size of ∼300 nm with special nanotwinned boundaries and an extremely smooth surface of ∼3-4 nm are strongly desired for better reflectivity. Further, on the basis of these microscopy results, suggestions on light extraction optimization are given to improve the performance of GaN-based blue VLEDs. Our findings enable fresh and deep understanding of performance-microstructure correlation of LEDs on the nanoscale, providing guidance to the design and manufacture of high-performance LED devices.

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Section: Resultsmentioning

confidence: 93%

Section: Experimental Results and Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Insights into the Silver Reflection Layer of a Vertical LED for Light Emission Optimization

Khan¹,

Chen²,

Qu³

et al. 2017

ACS Appl. Mater. Interfaces

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“…Wafer bonding is an effective method to limit defects at the bonding interface, overcome the lattice mismatch in hetero-epitaxial growth, and realize new multi-layer structure to fabricate high-quality optoelectronic devices. [22][23][24] In this way, GaN-based LED can be transferred to all kinds of dissimilar substrates, such as polycrystalline metal, glass, silicon, and even plastics.…”

Section: Methodsmentioning

confidence: 99%

Damage-Free Transfer of GaN-Based Light-Emitting Devices and Reuse of Sapphire Substrate

Zhang

Luo

2020

ECS J. Solid State Sci. Technol.

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Gallium nitride (GaN) based semiconductors have been gaining worldwide attention in optoelectronics application, notably information displays and solid-state lighting. GaN light-emitting diodes (LEDs) epilayers are typically grown on sapphire substrates with metal-organic chemical vapor deposition (MOCVD) technique due to the absence of native nitride substrates. In this paper, the mesh-patterned sapphire substrates are fabricated to speed up the laser lift-off efficiency for the separation of GaN films from sapphire substrates. Damage-free GaN thin films fabricated on the sapphire substrates were successfully released and transferred onto Si substrates with sufficient quality through a Ti/Pt/Au/In bonding and subsequent laser lift-off processes. The GaN film mounted on Si substrates exhibits almost no attenuation in PL intensity before and after its transfer. The released sapphire substrate can be reprocessed by annealing & chemical mechanical polishing (CMP) process for reuse as epitaxial substrate with considerable cost reduction, featuring a comparable photoluminescence performance with fresh sapphire substrates.

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“…LEDs have been regarded as a promising candidate for lighting technology because of their application in back lighting in liquid-crystal displays, full-color display, traffic light lamps, and solid-state lighting. [1][2][3][4][5] It is due to the wide band gap (3.4 eV), high breakdown voltage (>5 × 10 6 V cm −1 ), unique chemical and thermal stability possessed by GaN. Many researches widely study pad-extended on chip (PEC) LEDs because that pad extension chip improves lightextraction efficiency better than conventional GaN-LEDs.…”

Section: Introductionmentioning

confidence: 99%

Reliability improvement of pad-extended on chip light-emitting diodes using an ultra-thin passivation layer

Chang

Tseng

et al. 2018

Jpn. J. Appl. Phys.

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The pad-extended on chip (PEC) light-emitting diodes (LEDs) were fabricated and characterized by using an ultra-thin silicon oxide (SiO 2 ) film as a passivation layer. The SiO 2 thin film was deposited on the GaN mesa edge using plasma-enhanced chemical vapor deposition (PECVD) by varying deposition temperature from 150 to 350 °C. Atomic force microscopy (AFM), a scanning electron microscope (SEM) and leakage current were employed to analyze the influence of deposition temperature on the structural properties of SiO 2 films. AFM measurements demonstrate that the SiO 2 surface roughness was larger at a lower deposition temperature than a higher temperature. Forward voltage (V f ) characteristics of these PEC LEDs were detected and recorded for continuous ten thousand probe times. The curve of V f remained stable at temperatures of 150, 200 and 250 °C. A metal-insulator-metal structure using 250 °C-deposited SiO 2 as the dielectric indicates the leakage current density was close to 10 −8 A cm −2 with the minimum one lower than 10 −12 A cm −2 . The relative dielectric constant of the SiO 2 (20 nm) was 3.65. The ultra-thin SiO 2 film efficiently passivated the GaN mesa edge and prevented charge accumulation at the surface. Reliability has been improved for PEC LEDs using the ultra-thin SiO 2 film as a passivation layer.

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On the metallic bonding of GaN-based vertical light-emitting diode

Cited by 9 publications

References 62 publications

Insights into the Silver Reflection Layer of a Vertical LED for Light Emission Optimization

Insights into the Silver Reflection Layer of a Vertical LED for Light Emission Optimization

Damage-Free Transfer of GaN-Based Light-Emitting Devices and Reuse of Sapphire Substrate

Reliability improvement of pad-extended on chip light-emitting diodes using an ultra-thin passivation layer

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