Performance Improvement of AlGaN-Based Deep Ultraviolet Light-Emitting Diodes With Step-Like Quantum Barriers

Xing, Chong; Yu, Huabin; Ren, Zhongjie; Zhang, Haochen; Dai, Jiangnan; Chen, Chang; Sun, Haiding

doi:10.1109/jqe.2019.2956344

Cited by 22 publications

(19 citation statements)

References 37 publications

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“…Also, inverted-V-shaped quantum barriers or thinner graded quantum barriers of AlGaN-based MQWs were found to be useful for the application in DUV LEDs 43 , 44 . Similarly, AlGaN-based DUV LED structure with unique step-like quantum barriers in MQWs has been proposed to overcome the electron`s overshooting toward the p-side 45 . However, such experimental studies of graded Al composition in electron blocking layer or in p-AlGaN HSL of 304 nm-band UVB emitters are still rare 8 , 23 – 26 .…”

Section: Resultsmentioning

confidence: 99%

Achieving 9.6% efficiency in 304 nm p-AlGaN UVB LED via increasing the holes injection and light reflectance

Khan

Maeda

Yun

et al. 2022

Sci Rep

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Crystal growth of eco-friendly, ultrawide bandgap aluminium gallium nitride (AlGaN) semiconductor-based ultraviolet-B (UVB) light-emitting diodes (LEDs) hold the potential to replace toxic mercury-based ultraviolet lamps. One of the major drawbacks in the utilisation of AlGaN-based UVB LEDs is their low efficiency of about 6.5%. The study investigates the influence of Al-graded p-type multi-quantum-barrier electron-blocking-layer (Al-grad p-MQB EBL) and Al-graded p-AlGaN hole source layer (HSL) on the generation and injection of 3D holes in the active region. Using the new UVB LED design, a significant improvement in the experimental efficiency and light output power of about 8.2% and 36 mW is noticed. This is accomplished by the transparent nature of Al-graded Mg-doped p-AlGaN HSL for 3D holes generation and p-MQB EBL structure for holes transport toward multi-quantum-wells via intra-band tunnelling. Based on both the numerical and experimental studies, the influence of sub-nanometre scale Ni film deposited underneath the 200 nm-thick Al-film p-electrode on the optical reflectance in UVB LED is investigated. A remarkable improvement in the efficiency of up to 9.6% and light output power of 40 mW, even in the absence of standard package, flip-chip, and resin-like lenses, is achieved on bare-wafer under continuous-wave operation at room temperature. The enhanced performance is attributed to the use of Al-graded p-MQB EBL coupled with softly polarised p-AlGaN HSL and the highly reflective 0.4 nm-thick Ni and 200 nm-thick Al p-electrode in the UVB LED. This research study provides a new avenue to improve the performance of high-power p-AlGaN-based UVB LEDs and other optoelectronic devices in III–V semiconductors.

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Section: Resultsmentioning

confidence: 99%

Achieving 9.6% efficiency in 304 nm p-AlGaN UVB LED via increasing the holes injection and light reflectance

Khan

Maeda

Yun

et al. 2022

Sci Rep

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“…The final optimization results show that the optimal light output rate is 16.47% for the InGaN model and 7.43% for the AlGaN model, which is an improvement compared to the 4% light output rate in the blue band and 6% in the ultraviolet band of flat-panel LED, [52][53][54] proving the effectiveness of the single-period PhC structure.…”

Section: 21mentioning

confidence: 92%

Enhancing light extraction efficiency of GaN LED by combining complex‐period photonic crystals with doping

Chen

Wang

2023

J Am Ceram Soc.

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The light extraction efficiency (LEE) of GaN‐based light‐emitting diodes (LEDs) was limited by intense total internal reflection and the photothermal effect. In order to solve this problem, a method to synergistically control the LEE of GaN‐based LEDs by combining the complex‐period photonic crystals (PhCs) with M (M = Al, In) material doping is proposed. The forbidden band width of two‐dimensional (2D) PhC array, three‐dimensional (3D) LED model, M doping, and electromagnetic field distribution are investigated respectively. By doping the M, the LED emission wavelength range is regulated to achieve the dual‐band emission. Furthermore, a triangular complex‐period photonic structure is introduced to establish stacked or etched PhCs models. By combining the plane wave expansion and finite difference time domain algorithm, the structural parameters of PhCs and M concentration dependent LEE are investigated, and the electromagnetic field distribution is explored also. The results show that the optimal LEEs can be achieved are 19.08% and 13.96% for blue light and ultraviolet, respectively, which are larger than that of traditional flat‐panel LED (4%). This work provides theoretical results and technical support for the design of LEDs with high luminous efficiency.

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“…(C) In addition to optimizing the substrate and Al x Ga 1-x N ternary mixed crystal, it is also necessary to improve the epitaxial structure of the quantum well in the active region, so that the holes and electrons in the active region are effectively constrained, and the overlap of the hole-electron wave function is improved. The use of stepped Al component barrier regions in quantum wells can effectively improve the recombination efficiency of holes and electrons [40,41]. Studies have shown that the use of GaN/AlN structures in quantum wells can significantly improve the quantum efficiency [42].…”

Section: Immature Epitaxial Technology Of Highmentioning

confidence: 99%

Perspectives on UVC LED: Its Progress and Application

et al. 2021

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High-quality epitaxial layers are directly related to internal quantum efficiency. The methods used to design such epitaxial layers are reviewed in this article. The ultraviolet C (UVC) light-emitting diode (LED) epitaxial layer structure exhibits electron leakage; therefore, many research groups have proposed the design of blocking layers and carrier transportation to generate high electron–hole recombination rates. This also aids in increasing the internal quantum efficiency. The cap layer, p-GaN, exhibits high absorption in deep UV radiation; thus, a small thickness is usually chosen. Flip chip design is more popular for such devices in the UV band, and the main factors for consideration are light extraction and heat transportation. However, the choice of encapsulation materials is important, because unsuitable encapsulation materials will be degraded by ultraviolet light irradiation. A suitable package design can account for light extraction and heat transportation. Finally, an atomic layer deposition Al2O3 film has been proposed as a mesa passivation layer. It can provide a low reverse current leakage. Moreover, it can help increase the quantum efficiency, enhance the moisture resistance, and improve reliability. UVC LED applications can be used in sterilization, water purification, air purification, and medical and military fields.

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Performance Improvement of AlGaN-Based Deep Ultraviolet Light-Emitting Diodes With Step-Like Quantum Barriers

Cited by 22 publications

References 37 publications

Achieving 9.6% efficiency in 304 nm p-AlGaN UVB LED via increasing the holes injection and light reflectance

Achieving 9.6% efficiency in 304 nm p-AlGaN UVB LED via increasing the holes injection and light reflectance

Enhancing light extraction efficiency of GaN LED by combining complex‐period photonic crystals with doping

Perspectives on UVC LED: Its Progress and Application

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