Light Extraction Efficiency Optimization of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes

Wan, Hui; Zhou, Shengjun; Lan, Shuyu; Chen, Gui

doi:10.1149/2162-8777/ab85c0

Cited by 21 publications

(8 citation statements)

References 41 publications

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“…The NPSS improves TM-polarized light extraction reflected by the Al/Si inclined sidewall. 33 Figure 4c shows the EQE trend of the measured devices under CW biasing conditions. All of the UV-LED devices show efficiency droop at high injection currents.…”

Section: Resultsmentioning

confidence: 99%

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Breaking the Transverse Magnetic-Polarized Light Extraction Bottleneck of Ultraviolet-C Light-Emitting Diodes Using Nanopatterned Substrates and an Inclined Reflector

et al. 2022

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AlGaN-based light-emitting diodes (LEDs) operating in the deep-ultraviolet (UV-C) spectral range (210−280 nm) exhibit extremely low external quantum efficiency, primarily due to the presence of large threading dislocations and extremely low transverse magnetic (TM) light extraction efficiency.Here, we have demonstrated that such critical issues can be potentially addressed by using AlGaN quantum-well heterostructures grown on a hexagonal nanopatterned sapphire substrate (NPSS) and a flip-chip-bonded inclined Al mirror. Our finite-difference time domain-based numerical analysis confirms that the maximum achievable efficiency is limited by the poor light extraction efficiency due to the extremely low TM-polarized emission. In our experiment, with the usage of a meticulously designed hexagonal NPSS and an inclined Al side wall mirror (>90% reflective in the UV-C wavelength), the AlGaN quantum-well UV-C LEDs showed nearly 20% improvement in the light output power and efficiency compared to the conventional flat flip-chip LEDs. The UV-C LEDs operating at ∼275 nm exhibit a maximum output power of ∼25 mW at 150 mA, a peak external quantum efficiency of ∼4.7%, and a wall plug efficiency of ∼3.25% at 15 mA under continuous wave (CW) conditions. The presented approach opens up new opportunities to increase the extraction of UV light in the challenging spectral range by using properly designed patterned substrates and an engineered Al reflector.

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Section: Resultsmentioning

confidence: 99%

“…Previously, it was demonstrated that the NPSS could significantly enhance the UV-LED light extraction from sidewalls by scattering at the interface of sapphire and AlN. The NPSS improves TM-polarized light extraction reflected by the Al/Si inclined sidewall …”

Section: Resultsmentioning

confidence: 99%

Breaking the Transverse Magnetic-Polarized Light Extraction Bottleneck of Ultraviolet-C Light-Emitting Diodes Using Nanopatterned Substrates and an Inclined Reflector

et al. 2022

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Section: Influence Of Structural Parameters Of Pss On Led Propertiesmentioning

confidence: 93%

“…In our previous study, we have investigated the LEE of DUV LEDs using FDTD method. 132 The results showed that NPSS could enhance the LEE of TM-polarized lights significantly, as compared to FSS. Furthermore, the LEE of flip-chip LED on NPSS was estimated to be about 15%, which was ∼50% higher than that of flip-chip DUV LED with rough n-AlGaN surface (Fig.…”

Section: Influence Of Structural Parameters Of Pss On Led Propertiesmentioning

confidence: 93%

Application of patterned sapphire substrate for III-nitride light-emitting diodes

Zhou

Zhao

et al. 2022

Nanoscale

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“…For example, growing AlN film on the SiC substrate can effectively reduce the dislocation of AlN due to the similar lattice matching between the SiC substrate and AlN epitaxial layer, but the expensive SiC substrate increases the cost of producing DUV-LEDs [12,13]. In addition, the high-quality AlN epitaxial layers can be obtained on the nanopatterned sapphire substrate (NPSS), which effectively improves the internal quantum efficiency of DUV-LEDs [14][15][16]. However, due to the large migration barrier of Al atoms on the surface of NPSS, the growth mode of Al atoms follows the 3D Volmer-Weber growth mode.…”

Section: Introductionmentioning

confidence: 99%

High quality AlN film assisted by graphene/sputtered AlN buffer layer for deep-ultraviolet-LED

Ning

Zhang

et al. 2023

Nanotechnology

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The advantages of van der Waals epitaxial nitrides have become a research hot topic. It is worth noting that graphene plays an important role in the research of epitaxial AlN epitaxial layer. In this work, we demonstrate a method to obtain high-quality and low-dislocation AlN epitaxial layer by combining graphene and sputtered AlN as the nucleation layer on the C-sapphire substrate via metal organic chemical vapor deposition (MOCVD), and successfully fabricated a 277 nm AlGaN-based deep ultraviolet light emitting diode (DUV-LED) based on the obtained AlN epitaxial layer. The presence of graphene promotes the stress release of AlN. Compared with the AlN epitaxial layer directly grown on graphene/sapphire substrate, the exist of sputtered AlN/graphene nucleation layer facilitates most of the threading dislocations in AlN can annihilate each other in the range of about 100 nm. Thus, as grown AlN epitaxial layer shows the decreasing of the screw dislocation from 2.31 × 109 to 2.08 × 108 cm-2 significantly. We manufacture an DUV-LED with 277nm emission wavelength by using high-quality AlN films, which shows that magnitude of the leakage current is only on the order of nanoamperes and the forward turn on voltage is 3.5 V at room temperature. This study provides a meaningful strategy to achieve high-quality AlN film and high-performance DUV-LED.

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Light Extraction Efficiency Optimization of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes

Cited by 21 publications

References 41 publications

Breaking the Transverse Magnetic-Polarized Light Extraction Bottleneck of Ultraviolet-C Light-Emitting Diodes Using Nanopatterned Substrates and an Inclined Reflector

Breaking the Transverse Magnetic-Polarized Light Extraction Bottleneck of Ultraviolet-C Light-Emitting Diodes Using Nanopatterned Substrates and an Inclined Reflector

Application of patterned sapphire substrate for III-nitride light-emitting diodes

High quality AlN film assisted by graphene/sputtered AlN buffer layer for deep-ultraviolet-LED

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