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Journal articles on the topic 'AlGaN/AlGaN Duv Leds'

Author: Grafiati

Published: 4 June 2025

Last updated: 14 July 2025

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Wang, Tien-Yu, Wei-Chih Lai, Syuan-Yu Sie, Sheng-Po Chang, Cheng-Huang Kuo, and Jinn-Kong Sheu. "Deep Ultraviolet AlGaN-Based Light-Emitting Diodes with p-AlGaN/AlGaN Superlattice Hole Injection Structures." Processes 9, no. 10 (2021): 1727. http://dx.doi.org/10.3390/pr9101727.

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The p-AlGaN/AlGaN superlattice (SL) hole injection structure was introduced into deep ultraviolet (DUV) light-emitting diodes (LEDs) to enhance their performances. The period thicknesses of the p-Al0.8Ga0.2N/Al0.48Ga0.52N SLs affected the performances of the DUV LEDs. The appropriate period thickness of the p-Al0.8Ga0.2N/Al0.48Ga0.52N SL may enhance the hole injection of DUV LEDs. Therefore, compared with the reference LEDs, the DUV LEDs with the 10-pair Al0.8Ga0.2N (1 nm)/Al0.48Ga0.52N (1 nm) SL presented forward voltage reduction of 0.23 V and light output power improvement of 15% at a current of 350 mA. Furthermore, the 10-pair Al0.8Ga0.2N (1 nm)/Al0.48Ga0.52N (1 nm) SL could slightly suppress the Auger recombination and current overflow of the DUV LEDs in a high-current operation region. In addition to improved carrier injection, the DUV LEDs with the p-Al0.8Ga0.2N/Al0.48Ga0.52N SL hole injection structure showed reduced light absorption at their emission wavelength compared with the reference LEDs. Therefore, the DUV LEDs with p-Al0.8Ga0.2N/Al0.48Ga0.52N SL may exhibit better light extraction efficiency than the reference LEDs. The enhancement of p-Al0.8Ga0.2N (1 nm)/Al0.48Ga0.52N (1 nm) SL may contribute to improvements in light extraction and hole injection.

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Gong, Mingfeng, Xuejiao Sun, Cheng Lei, et al. "Study on the Degradation Performance of AlGaN-Based Deep Ultraviolet LEDs under Thermal and Electrical Stress." Coatings 14, no. 7 (2024): 904. http://dx.doi.org/10.3390/coatings14070904.

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AlGaN-based deep-ultraviolet (DUV) LEDs could realize higher optical power output when adopting a p-AlGaN contact layer instead of a p-GaN contact layer. However, this new type DUV LEDs exhibit poor reliability. Thus, this study thoroughly investigates the degradation behaviors of AlGaN-based DUV LEDs with a p-AlGaN contact layer through different aging tests, including single thermal stress, single electrical stress with air-cooling, single electrical stress, and thermoelectric complex stress. It can be found that both high temperature and large working current play crucial roles in accelerating the degradation of optoelectronic properties of the DUV LEDs, and the single high thermal stress without electrical stress can also bring obvious performance degradation to the DUV LEDs, which is a significantly different finding from previous studies. This is because thermal stress on DUV LED could bring some metal electrode elements entering the p-AlGaN layer. Thus, the degradation of optical and electrical properties under the thermal and electrical stress could be not only attributed to the degradation of the device’s ohmic contacts, but also due to the metal electrode elements entering the p-AlGaN layer through thermal diffusion, leading to the generation of tunneling current and the generation of defects within or around the active region. Despite that the peak wavelengths of the DUV LEDs remained stable, the turn-on voltage and series resistance increased. Particularly worth mentioning is that the value of the optical power degradation under thermoelectric conditions is larger than the sum of the single thermal and single electrical optical power degradation, which is a result of the mutual reinforcement of thermal and electrical stresses to exacerbate the defect generation and ohmic contact degradation. Based on the study above, preparing p-AlGaN layers with hyperfine gradient aluminum fractions and reducing the junction temperature may help to improve the reliability of AlGaN-based DUV LEDs with the p-AlGaN contact layer.

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Xu, Ruiqiang, Qiushi Kang, Youwei Zhang, Xiaoli Zhang, and Zihui Zhang. "Research Progress of AlGaN-Based Deep Ultraviolet Light-Emitting Diodes." Micromachines 14, no. 4 (2023): 844. http://dx.doi.org/10.3390/mi14040844.

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AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) have great application prospects in sterilization, UV phototherapy, biological monitoring and other aspects. Due to their advantages of energy conservation, environmental protection and easy miniaturization realization, they have garnered much interest and been widely researched. However, compared with InGaN-based blue LEDs, the efficiency of AlGaN-based DUV LEDs is still very low. This paper first introduces the research background of DUV LEDs. Then, various methods to improve the efficiency of DUV LED devices are summarized from three aspects: internal quantum efficiency (IQE), light extraction efficiency (LEE) and wall-plug efficiency (WPE). Finally, the future development of efficient AlGaN-based DUV LEDs is proposed.

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Băjenescu, Titu-Marius I. "DEEP ULTRAVIOLET LIGHT EMITTING DIODES (DUV LEDS)." Journal of Engineering Science XXV (2) (June 15, 2018): 6–19. https://doi.org/10.5281/zenodo.2559253.

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There are a variety of applications for devices that extend into the deep-UV, including biological agent detection and optical storage. The nitride material system is a set of semiconducting compounds that have wavelengths that span a broad range, from yellow to deep-UV. AlGaN has a direct bandgap that extends into the deep-UV range; the device-quality material, is deposited epitaxially using metalorganic chemical vapor deposition on sapphire substrates. 

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Wang, Tien-Yu, Wei-Chih Lai, Qiao-Ju Xie, et al. "The influences of AlGaN barrier epitaxy in multiple quantum wells on the optoelectrical properties of AlGaN-based deep ultra-violet light-emitting diodes." RSC Advances 13, no. 8 (2023): 5437–43. http://dx.doi.org/10.1039/d2ra07368d.

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Liu, Cheng, Bryan Melanson, and Jing Zhang. "AlGaN-Delta-GaN Quantum Well for DUV LEDs." Photonics 7, no. 4 (2020): 87. http://dx.doi.org/10.3390/photonics7040087.

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AlGaN-delta-GaN quantum well (QW) structures have been demonstrated to be good candidates for the realization of high-efficiency deep-ultraviolet (DUV) light-emitting diodes (LEDs). However, such heterostructures are still not fully understood. This study focuses on investigation of the optical properties and efficiency of the AlGaN-delta-GaN QW structures using self-consistent six-band k⸱p modelling and finite difference time domain (FDTD) simulations. Structures with different Al contents in the AlxGa1−xN sub-QW and AlyGa1−yN barrier regions are examined in detail. Results show that the emission wavelength (λ) can be engineered through manipulation of delta-GaN layer thickness, sub-QW Al content (x), and barrier Al content (y), while maintaining a large spontaneous emission rate corresponding to around 90% radiative recombination efficiency (ηRAD). In addition, due to the dominant transverse-electric (TE)-polarized emission from the AlGaN-delta-GaN QW structure, the light extraction efficiency (ηEXT) is greatly enhanced when compared to a conventional AlGaN QW. Combined with the large ηRAD, this leads to the significant enhancement of external quantum efficiency (ηEQE), indicating that AlGaN-delta-GaN structures could be a promising solution for high-efficiency DUV LEDs.

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Chang, Jih-Yuan, Man-Fang Huang, Chih-Yung Huang, Shih-Chin Lin, Ching-Chiun Wang, and Yen-Kuang Kuo. "Band-Engineered Structural Design of High-Performance Deep-Ultraviolet Light-Emitting Diodes." Crystals 11, no. 3 (2021): 271. http://dx.doi.org/10.3390/cryst11030271.

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In this study, systematic structural design was investigated numerically to probe into the cross-relating influences of n-AlGaN layer, quantum barrier (QB), and electron-blocking layer (EBL) on the output performance of AlGaN deep-ultraviolet (DUV) light-emitting diodes (LEDs) with various Al compositions in quantum wells. Simulation results show that high-Al-composition QB and high-Al-composition EBL utilized separately are beneficial for the enhancement of carrier confinement, while the wall-plug efficiency (WPE) degrades dramatically if both high-Al-composition QB and EBL are existing in a DUV LED structure simultaneously. DUV LEDs may be of great optical performance with appropriate structural design by fine-tuning the material parameters in n-AlGaN layer, QB, and EBL. The design curves provided in this paper can be very useful for the researchers in developing the DUV LEDs with a peak emission wavelength ranging from 255 nm to 285 nm.

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Amano, Hiroshi, Masataka Imura, Motoaki Iwaya, Satoshi Kamiyama, and Isamu Akasaki. "AlN and AlGaN by MOVPE for UV Light Emitting Devices." Materials Science Forum 590 (August 2008): 175–210. http://dx.doi.org/10.4028/www.scientific.net/msf.590.175.

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The fundamental growth issues of AlN and AlGaN on sapphire and SiC using metalorganic vapor phase epitaxy, particularly the growth of AlN and AlGaN on a groove-patterned template are reviewed. In addition, the conductivity control of AlGaN is shown. The conductivity control of p-type AlGaN, particularly the realization of a high hole concentration, is essential for realizing high-efficiency UV and DUV LEDs and LDs.

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Yang, Sipan, Miao He, Jianchang Yan, et al. "Enhanced electrical performance by modulation-doping in AlGaN-based deep ultraviolet light-emitting diodes." Modern Physics Letters B 33, no. 08 (2019): 1950088. http://dx.doi.org/10.1142/s021798491950088x.

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Through the silicon modulation-doping (MD) growth method, the electrical performance of AlGaN-based deep ultraviolet light-emitting diodes (DUV-LEDs) is improved by replacing the commonly uniform-doped (UD) method of n-AlGaN layer. The electroluminescence characterisic measurements demonstrate the MD growth method could effectively enhance the light emission intensity. Both the forward voltage and reverse leakage current of the MD samples are obviously reduced compared to those of the UD sample. Due to the existence of periodic Si-MD superlattices in n-AlGaN layers, which may behave like a series of capacitors, the built-in electric fields are formed. Both the measured capacitance–voltage (C–V) characteristics, and related photoluminescence (PL) intensity with the Si-MD growth method are enhanced. In detail, the effects of these capacitors can enhance the peak internal capacitance up to 370 pF in the MD sample, whereas the UD sample is only 180 pF. The results also mean that with better current spreading ability in the MD sample, the MD processes can effectively enhance the efficiency and reliability of DUV-LEDs. Thus, the investigations of the Si-MD growth methods may be useful for improving the electrical performance of DUV-LEDs in future works. Meanwhile, this investigation may partly suggest the minor crystalline quality improvements in the epi-layers succeeding the MD n-AlGaN layer.

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Nagasawa, Yosuke, and Akira Hirano. "A Review of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes on Sapphire." Applied Sciences 8, no. 8 (2018): 1264. http://dx.doi.org/10.3390/app8081264.

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This paper reviews the progress of AlGaN-based deep-ultraviolet (DUV) light emitting diodes (LEDs), mainly focusing in the work of the authors’ group. The background to the development of the current device structure on sapphire is described and the reason for using a (0001) sapphire with a miscut angle of 1.0° relative to the m-axis is clarified. Our LEDs incorporate uneven quantum wells (QWs) grown on an AlN template with dense macrosteps. Due to the low threading dislocation density of AlGaN and AlN templates of about 5 × 108/cm2, the number of nonradiative recombination centers is decreased. In addition, the uneven QW show high external quantum efficiency (EQE) and wall-plug efficiency, which are considered to be boosted by the increased internal quantum efficiency (IQE) by enhancing carrier localization adjacent to macrosteps. The achieved LED performance is considered to be sufficient for practical applications. The advantage of the uneven QW is discussed in terms of the EQE and IQE. A DUV-LED die with an output of over 100 mW at 280–300 nm is considered feasible by applying techniques including the encapsulation. In addition, the fundamental achievements of various groups are reviewed for the future improvements of AlGaN-based DUV-LEDs. Finally, the applications of DUV-LEDs are described from an industrial viewpoint. The demonstrations of W/cm2-class irradiation modules are shown for UV curing.

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Xiao, Shudan, Huabin Yu, Hongfeng Jia, et al. "Performance evaluation of tunnel junction-based N-polar AlGaN deep-ultraviolet light-emitting diodes." Optics Letters 47, no. 16 (2022): 4187. http://dx.doi.org/10.1364/ol.467685.

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In this study, an N-polar AlGaN-based deep-ultraviolet (DUV) light-emitting diode (LED) incorporating a tunnel junction (TJ) as the p-side contact layer, named the N-TJ-LED, was proposed. Compared with regular N-polar LEDs (N-LEDs) with a p-GaN contact layer, the N-TJ-LEDs exhibited 50% enhanced internal quantum efficiency, 2.7 times higher light output power at an injection current of 40 mA, and dramatically reduced turn-on voltage. In addition, it was found that the N-TJ-LED can still maintain outstanding device performance at a low p-type doping level in the electron blocking layer and p-AlGaN current injection layer, significantly outperforming the regular N-LED. All these performance enhancements are derived from the higher electron and hole concentration in the active region of the N-TJ-LED, thanks to the TJ-facilitated efficient hole injection and effective electron blocking in the device. The results demonstrated in this work provide an effective strategy for the future experimental optimization of N-polar AlGaN-based DUV LEDs.

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Pai, Yung-Min, Chih-Hao Lin, Chun-Fu Lee, et al. "Enhancing the Light-Extraction Efficiency of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes by Optimizing the Diameter and Tilt of the Aluminum Sidewall." Crystals 8, no. 11 (2018): 420. http://dx.doi.org/10.3390/cryst8110420.

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To realize high-efficiency AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs), enhancing their light-extraction efficiency (LEE) is crucial. This paper proposes an aluminum-based sidewall reflector structure that could replace the conventional ceramic-based packaging method. We design optimization simulations and experimental results demonstrated the light power output could be enhanced 18.38% of DUV-LEDs packaged with the aluminum-based sidewall.

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Kang, Chieh-Yu, Chih-Hao Lin, Tingzhu Wu, Po-Tsung Lee, Zhong Chen, and Hao-Chung Kuo. "A Novel Liquid Packaging Structure of Deep-Ultraviolet Light-Emitting Diodes to Enhance the Light-Extraction Efficiency." Crystals 9, no. 4 (2019): 203. http://dx.doi.org/10.3390/cryst9040203.

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To realize high-efficiency, AlGaN-based, deep-ultraviolet light-emitting diodes (DUV-LEDs), enhancing their light-extraction efficiency and reducing thermal resistance is very crucial. We proposed a liquid packaging structure that could enhance optical power by 27.2% and 70.7% for flat type and lens type 281-nm DUV-LEDs, respectively. A significant improvement effect at different wavelengths, such as 268 nm and 310 nm, was also observed. Furthermore, using the liquid packaging structure, the thermal resistance was reduced by 30.3% compared to the conventional structure. Finally, the reliability of liquid packaging DUV-LEDs was tested. The light output maintenance of liquid packaging DUV-LEDs was compared to the conventional structure.

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Feng, Zhe Chuan, Ming Tian, Xiong Zhang, et al. "Deep Ultraviolet Excitation Photoluminescence Characteristics and Correlative Investigation of Al-Rich AlGaN Films on Sapphire." Nanomaterials 14, no. 21 (2024): 1769. http://dx.doi.org/10.3390/nano14211769.

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AlGaN is attractive for fabricating deep ultraviolet (DUV) optoelectronic and electronic devices of light-emitting diodes (LEDs), photodetectors, high-electron-mobility field-effect transistors (HEMTs), etc. We investigated the quality and optical properties of AlxGa1−xN films with high Al fractions (60–87%) grown on sapphire substrates, including AlN nucleation and buffer layers, by metal–organic chemical vapor deposition (MOCVD). They were initially investigated by high-resolution X-ray diffraction (HR-XRD) and Raman scattering (RS). A set of formulas was deduced to precisely determine x(Al) from HR-XRD data. Screw dislocation densities in AlGaN and AlN layers were deduced. DUV (266 nm) excitation RS clearly exhibits AlGaN Raman features far superior to visible RS. The simulation on the AlGaN longitudinal optical (LO) phonon modes determined the carrier concentrations in the AlGaN layers. The spatial correlation model (SCM) analyses on E2(high) modes examined the AlGaN and AlN layer properties. These high-x(Al) AlxGa1−xN films possess large energy gaps Eg in the range of 5.0–5.6 eV and are excited by a DUV 213 nm (5.8 eV) laser for room temperature (RT) photoluminescence (PL) and temperature-dependent photoluminescence (TDPL) studies. The obtained RTPL bands were deconvoluted with two Gaussian bands, indicating cross-bandgap emission, phonon replicas, and variation with x(Al). TDPL spectra at 20–300 K of Al0.87Ga0.13N exhibit the T-dependences of the band-edge luminescence near 5.6 eV and the phonon replicas. According to the Arrhenius fitting diagram of the TDPL spectra, the activation energy (19.6 meV) associated with the luminescence process is acquired. In addition, the combined PL and time-resolved photoluminescence (TRPL) spectroscopic system with DUV 213 nm pulse excitation was applied to measure a typical AlGaN multiple-quantum well (MQW). The RT TRPL decay spectra were obtained at four wavelengths and fitted by two exponentials with fast and slow decay times of ~0.2 ns and 1–2 ns, respectively. Comprehensive studies on these Al-rich AlGaN epi-films and a typical AlGaN MQW are achieved with unique and significant results, which are useful to researchers in the field.

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Wang, Yong, Zihui Zhang, Long Guo, et al. "Calculating the Effect of AlGaN Dielectric Layers in a Polarization Tunnel Junction on the Performance of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes." Nanomaterials 11, no. 12 (2021): 3328. http://dx.doi.org/10.3390/nano11123328.

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In this work, AlGaN-based deep-ultraviolet (DUV) light-emitting diodes (LEDs) with AlGaN as the dielectric layers in p+-Al0.55Ga0.45N/AlGaN/n+-Al0.55Ga0.45N polarization tunnel junctions (PTJs) were modeled to promote carrier tunneling, suppress current crowding, avoid optical absorption, and further enhance the performance of LEDs. AlGaN with different Al contents in PTJs were optimized by APSYS software to investigate the effect of a polarization-induced electric field (Ep) on hole tunneling in the PTJ. The results indicated that Al0.7Ga0.3N as a dielectric layer can realize a higher hole concentration and a higher radiative recombination rate in Multiple Quantum Wells (MQWs) than Al0.4Ga0.6N as the dielectric layer. In addition, Al0.7Ga0.3N as the dielectric layer has relatively high resistance, which can increase lateral current spreading and enhance the uniformity of the top emitting light of LEDs. However, the relatively high resistance of Al0.7Ga0.3N as the dielectric layer resulted in an increase in the forward voltage, so much higher biased voltage was required to enhance the hole tunneling efficiency of PTJ. Through the adoption of PTJs with Al0.7Ga0.3N as the dielectric layers, enhanced internal quantum efficiency (IQE) and optical output power will be possible.

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Wang, Juan, Byung-Ryool Hyun, and Zhaojun Liu. "P‐11.7: Optimizing Chip Sidewall Inclined Angle and Thickness for Enhanced Light Extraction Efficiency in AlGaN‐based Deep Ultraviolet Micro‐LEDs." SID Symposium Digest of Technical Papers 55, S1 (2024): 1309–11. http://dx.doi.org/10.1002/sdtp.17349.

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In this paper, we systematically optimized the p‐type layers thickness and sidewall inclined angle of flip‐chip AlGaN‐based deep ultraviolet Micro‐LEDs using finite difference time‐domain (FDTD) method, aiming to maximize light extraction efficiency (LEE). It was found that due to the reflection of electrodes, variation in the thickness of p‐AlGaN and p‐GaN causes oscillations in the light extraction efficiency, which is caused by destructive interference and constructive interference. Additionally, we found that a 40° sidewall inclination angle yields the maximum LEE, with a 40% enhancement over the vertical sidewall. These simulation results present potential avenues for improving the LEE of DUV Micro‐LEDs.

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Liu, Kunzi, Li Chen, Tian Luo, et al. "Implementation of electron restriction layer in n-AlGaN toward balanced carrier distribution in deep ultraviolet light-emitting-diodes." Applied Physics Letters 121, no. 24 (2022): 241105. http://dx.doi.org/10.1063/5.0131013.

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The distribution of electrons and holes inside the multiple-quantum wells is highly non-uniform for AlGaN-based deep ultraviolet light-emitting diodes (DUV-LEDs) due to both insufficient hole injection and excessive electron leakage. A key factor to improve the quantum efficiency of DUV-LED is to reduce the proportion of hot electrons in n-AlGaN through carrier deceleration. In this work, we propose a structure design by introducing an additional Al0.55Ga0.45N/Al0.42Ga0.58N superlattice electron restriction layer between the active region and n-AlGaN for electron deceleration. The superlattice structure not only reduces the mobility of the electrons, which helps to balance the distribution of carriers in the active region, thus, promoting radiative recombination, but also facilitates the lateral transport of the electrons, thus, reducing the current crowding effect through band engineering. Low temperature electroluminescence analysis reveals that the improvement of quantum efficiency is due to both enhanced carrier injection efficiency and radiation recombination efficiency in the active region.

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Ye, Jiankun. "Doping and Defect Control in AlGaN-Based Deep Ultraviolet LEDs: Strategies for Enhanced Performance." Highlights in Science, Engineering and Technology 121 (December 24, 2024): 411–18. https://doi.org/10.54097/14ghge56.

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AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) are widely regarded for their potential in critical applications such as sterilization, water purification, and photolithography, operating in the 200-280 nm wavelength range. However, their performance remains limited by high defect densities, inefficient p-type doping, and low light extraction efficiency, which collectively reduce the external quantum efficiency (EQE). This paper provides a comprehensive review of current doping strategies, with an emphasis on optimizing both n-type and p-type conductivity, particularly in high-aluminum-content AlGaN. Moreover, the impact of threading dislocations and point defects on material properties is analyzed, alongside recent advancements in epitaxial growth methods like metal-organic chemical vapor deposition (MOCVD) aimed at reducing defect densities. Although significant progress has been made in defect management and doping efficiency, challenges remain, particularly in enhancing p-type doping activation. The paper concludes by suggesting future directions, including co-doping strategies and stress compensation layers, to further improve DUV LED performance and enable more efficient, commercially viable devices.

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So, Byeongchan, Jinwan Kim, Taemyung Kwak, et al. "Improved carrier injection of AlGaN-based deep ultraviolet light emitting diodes with graded superlattice electron blocking layers." RSC Advances 8, no. 62 (2018): 35528–33. http://dx.doi.org/10.1039/c8ra06982d.

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DUV-LEDs with a single EBL, graded EBL, and graded superlattice EBL were demonstrated using the high-temperature metal organic chemical vapor deposition system. A DUV-LED with a GSL-EBL showed improved carrier injection into the multi-quantum well region.

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Zhang, Aoxiang, Zhongqiu Xing, Yipu Qu, Fang Wang, Juin J. Liou, and Yuhuai Liu. "Optimization of AlGaN-based deep ultraviolet light emitting diodes with superlattice step doped electron blocking layers." Optics Express 32, no. 6 (2024): 10146. http://dx.doi.org/10.1364/oe.506106.

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The superlattice electron blocking layer (EBL) has been proposed to reduce the electron leakage of the deep ultraviolet light emitting diodes (DUV-LEDs). However, the hole transport is hindered by the barriers of EBL and the improvement of hole injection efficiency still suffers enormous challenges. The superlattice step doped (SLSD) EBL is proposed to improve the hole injection efficiency while enhancing the electron confinement capability. The SLSD EBL enhances the electron confinement capability by multi-reflection effects on the electron wave function. And a built-in electric field towards the active region is generated by superlattice step doping, which facilitates the transport of holes into the multiple quantum wells. The Advaced Physical Model of Semiconductor Devices (APSYS) software is used to simulate the DUV-LEDs with conventional EBL, superlattice EBL, superlattice doped EBL, and SLSD EBL. The results indicate that the SLSD EBL contributes to the increased electron concentration in the multiple quantum wells, the reduced electron leakage in the p-type region, the increased hole injection current, and the increased radiative recombination rate. When the current is 60 mA, the external quantum efficiency of DUV-LED with SLSD EBL is increased to 5.27% and the output power is increased to 13.81 mW. The SLSD EBL provides a valuable reference for solving the problems of serious electron leakage and insufficient hole injection of the DUV-LEDs.

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Hu, Xiaolong, Xu Liang, Lingyun Tang, and Wenjie Liu. "Enhanced Light Extraction Efficiency and Modulation Bandwidth of Deep-Ultraviolet Light-Emitting Diodes with Al Nanospheres." Crystals 12, no. 2 (2022): 289. http://dx.doi.org/10.3390/cryst12020289.

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Planar, nanopillar and Al nanosphere structure AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) were numerically investigated via a three-dimensional finite difference time domain (3D FDTD) method. The three types of DUV-LEDs were compared and analyzed in terms of light extraction efficiency (LEE), Purcell factor (FP) and modulation bandwidth. The results showed that nanopillar structure DUV-LEDs with optimal nanopillar height, width and spacing can enhance transverse electric (TE)-polarized LEE to 39.7% and transverse magnetic (TM)-polarized LEE to 4.4%. The remarkable improvement was mainly due to the increased scattering effect, decreased absorption of the p-GaN layer and total internal reflection (TIR) effect. After adopting the Al nanospheres, the TE-polarized modulation bandwidth was increased by 71 MHz and the TM-polarized LEE was enhanced approximately 4.3-fold as compared to the nanopillar LED structure, while the Al nanosphere diameter was 120 nm. The reasons for promotion are mainly attributed to the coupling behavior of diploe and localized surface plasmon induced by Al nanospheres. The designed structures provide a meaningful solution for realization of high-efficiency DUV-LEDs.

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Lim, Seungyoung, Tae-Soo Kim, Jaesang Kang, et al. "Anomalous Photocurrent Reversal Due to Hole Traps in AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes." Micromachines 13, no. 8 (2022): 1233. http://dx.doi.org/10.3390/mi13081233.

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The trap states and defects near the active region in deep-ultraviolet (DUV) light-emitting diodes (LED) were investigated through wavelength-dependent photocurrent spectroscopy. We observed anomalous photocurrent reversal and its temporal recovery in AlGaN-based DUV LEDs as the wavelength of illuminating light varied from DUV to visible. The wavelength-dependent photocurrent measurements were performed on 265 nm-emitting DUV LEDs under zero-bias conditions. Sharp near-band-edge (~265 nm) absorption was observed in addition to broad (300–800 nm) visible-range absorption peaks in the photocurrent spectrum, while the current direction of these two peaks were opposite to each other. In addition, the current direction of the photocurrent in the visible wavelength range was reversed when a certain forward bias was applied. This bias-induced current reversal displayed a slow recovery time (~6 h) when the applied forward voltage was removed. Furthermore, the recovery time showed strong temperature dependency and was faster as the sample temperature increased. This result can be consistently explained by the presence of hole traps at the electron-blocking layer and the band bending caused by piezoelectric polarization fields. The activation energy of the defect state was calculated to be 279 meV using the temperature dependency of the recovery time.

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Zhang, Chunyue, Ke Jiang, Xiaojuan Sun, and Dabing Li. "Recent Progress on AlGaN Based Deep Ultraviolet Light-Emitting Diodes below 250 nm." Crystals 12, no. 12 (2022): 1812. http://dx.doi.org/10.3390/cryst12121812.

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AlGaN based deep ultraviolet (DUV) light-emitting diodes (LEDs), especially with a wavelength below 250 nm, have great application potential in the fields of sterilization and disinfection, gas sensing, and other aspects. However, with the decrease of emission wavelength, performance collapse occurs and the external quantum efficiencies (EQE) of sub-250 nm LEDs are usually below 1% for a long time. Low efficiencies are resulted from problem accumulation of all aspects, including n/p-type doping and contacts, carrier confinements and transports, light extraction, etc. To achieve high EQE of sub-250 nm LEDs, problems and solutions need to be discussed. In this paper, the research progress, development bottlenecks, and corresponding solutions of sub-250 nm LEDs are summarized and discussed in detail.

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Zhu, Yifan, Huimin Lu, Jianping Wang, Tongjun Yu, Zizheng Li, and Yucheng Tian. "Enhanced light extraction by optimizing surface microstructure for AlGaN-based deep ultraviolet light emitting diodes with 265 and 280 nm emission." Journal of Applied Physics 132, no. 22 (2022): 225704. http://dx.doi.org/10.1063/5.0128213.

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In order to improve the light extraction for the deep ultraviolet light emitting diodes (DUV-LEDs), the surface microstructure based on a parabola cone array is used and optimized in work. In the optimization of the surface structure, inverse design based on a particle swarm optimization intelligent algorithm is applied to maximize the light extraction. The optimization results show that compared with the traditional planar structure, the optimized surface structure improves the light extraction efficiency by more than 200%. In addition, the influence of the designed surface microstructure on the light propagation is also explored by comparing the light field distribution and the light extraction process with the planar structure DUV-LEDs. It is revealed that the high aspect ratio of an array microstructure can change the light propagation and greatly expand the angle of a light escape cone. This effect can be maximized by the inverse design based on the intelligent algorithm, which has great potential in improving the light extraction of AlGaN-based DUV-LEDs.

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Lu, Shunpeng, Jiangxiao Bai, Hongbo Li, et al. "240 nm AlGaN-based deep ultraviolet micro-LEDs: size effect versus edge effect." Journal of Semiconductors 45, no. 1 (2024): 012504. http://dx.doi.org/10.1088/1674-4926/45/1/012504.

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Abstract 240 nm AlGaN-based micro-LEDs with different sizes are designed and fabricated. Then, the external quantum efficiency (EQE) and light extraction efficiency (LEE) are systematically investigated by comparing size and edge effects. Here, it is revealed that the peak optical output power increases by 81.83% with the size shrinking from 50.0 to 25.0 μm. Thereinto, the LEE increases by 26.21% and the LEE enhancement mainly comes from the sidewall light extraction. Most notably, transverse-magnetic (TM) mode light intensifies faster as the size shrinks due to the tilted mesa side-wall and Al reflector design. However, when it turns to 12.5 μm sized micro-LEDs, the output power is lower than 25.0 μm sized ones. The underlying mechanism is that even though protected by SiO2 passivation, the edge effect which leads to current leakage and Shockley-Read-Hall (SRH) recombination deteriorates rapidly with the size further shrinking. Moreover, the ratio of the p-contact area to mesa area is much lower, which deteriorates the p-type current spreading at the mesa edge. These findings show a role of thumb for the design of high efficiency micro-LEDs with wavelength below 250 nm, which will pave the way for wide applications of deep ultraviolet (DUV) micro-LEDs.

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Li, Zizheng, Huimin Lu, Jianping Wang, Yifan Zhu, Tongjun Yu, and Yucheng Tian. "Maximizing the Light Extraction Efficiency for AlGaN-Based DUV-LEDs with Two Optimally Designed Surface Structures under the Guidance of PSO." Crystals 12, no. 12 (2022): 1700. http://dx.doi.org/10.3390/cryst12121700.

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A novel method of utilizing an intelligent algorithm to guide the light extraction surface structure designing process for deep-ultraviolet light emitting diodes (DUV-LEDs) is proposed and investigated. Two kinds of surface structures based on the truncated pyramid array (TPA) and truncated cone array (TCA) are applied, which are expected to suppress the total internal reflection (TIR) effect and increase the light extraction efficiency (LEE). By addressing particle swarm optimization (PSO), the TPA and TCA microstructures constructed on the sapphire layer of the flip-chip DUV-LEDs are optimized. Compared to the conventional structure design method of parameter sweeping, this algorithm has much higher design efficiency and better optical properties. At the DUV wavelength of 280 nm, as a result, significant increases of 221% and 257% on the LEE are realized over the two forms of optimized surface structures. This approach provides another design path for DUV-LED light extraction structures.

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Matsubara, Taichi, Kengo Nagata, Maki Kushimoto, et al. "Sputtered polycrystalline MgZnO/Al reflective electrodes for enhanced light emission in AlGaN-based homojunction tunnel junction DUV-LED." Applied Physics Express 15, no. 4 (2022): 044001. http://dx.doi.org/10.35848/1882-0786/ac5acf.

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Abstract In this study, we enhanced the emission power of AlGaN-based tunnel junction deep-ultraviolet LEDs (TJ LEDs) by using a MgZnO and aluminum stacked structure as UV reflective electrodes on the anode side. The emission wavelength of the fabricated TJ LED was 284 nm, and the emission power was 57.3 mW at 63 A cm−2. The polycrystalline MgZnO enabled both conductivity and UV transmittance to be achieved, approximately doubling with a reflectance of the fabricated TJ LED at 284 nm compared to conventional TJ LED with Ti/Al. These factors contributed to the increased emission power of TJ LEDs.

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Ji, Yongchen, Mengran Liu, and Chao Liu. "Alleviated built-in electric field in the active region of AlGaN deep-ultraviolet light-emitting diodes with locally embedded p-i-n junctions." Applied Optics 61, no. 24 (2022): 6961. http://dx.doi.org/10.1364/ao.464029.

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The strong polarization-induced electric field in the multi-quantum well region reduces the radiative recombination rates by separating the electron and hole wave functions, which is one of the most detrimental factors that is to blame for the low luminous efficiency of AlGaN deep-ultraviolet light-emitting diodes (DUV LEDs). In this work, we redesigned the active region by incorporating Si and Mg doping at the vicinity of the quantum wells, forming a series of embedded p − i − n junctions in the multi-quantum well region. The additional electric field induced by the fixed charges from the embedded doping-induced junctions can effectively compensate for the intrinsic polarization-induced electric fields in the quantum well region and give rise to the improved overlap of hole and electron wave function, hence enhancing the radiative recombination rates and the external quantum efficiency and optical power of DUV LEDs. The mechanism behind the alleviated polarization electric field is comprehensively discussed and analyzed. The embedded p − i − n junctions can also alter the band diagram structure of the active region, decrease the effective barrier heights for holes, and diminish the electron leakage into the p -type region. In addition, different thicknesses and doping concentrations of the embedded p - and n - layers were designed, and their influence on the performance of DUV LEDs was numerically analyzed. The proposed structure with embedded p − i − n junctions provides an alternative way to achieve efficient DUV LEDs.

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Tan, Shuxin, Jicai Zhang, Takashi Egawa, and Gang Chen. "Influence of Quantum-Well Number and an AlN Electron Blocking Layer on the Electroluminescence Properties of AlGaN Deep Ultraviolet Light-Emitting Diodes." Applied Sciences 8, no. 12 (2018): 2402. http://dx.doi.org/10.3390/app8122402.

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The influence of quantum-well (QW) number on electroluminescence properties was investigated and compared with that of AlN electron blocking layer (EBL) for deep ultraviolet light-emitting diodes (DUV-LEDs). By increasing the QW number, the band emission around 265 nm increased and the parasitic peak around 304 nm was suppressed. From the theoretical calculation, the electron current overflowing to the p-type layer was decreased as the QW number increased under the same injection. Correspondingly, the light output power also increased. The increment of output power from 5 QWs to 10 QWs was less than that from 10 QWs to 40 QWs, which was very different from what has been reported for blue and near-UV LEDs. The parasitic peak was still observed even when the QW number increased to 40. However, it can be suppressed efficiently by 1 nm AlN EBL for LEDs with 5 QWs. The simulation showed that the insertion of a thin EBL increased the barrier height for electron overflow and the electron current in p-type layers decreased significantly. The results contributed to the understanding of behavior of electron overflow in DUV-LEDs.

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Zhao, Hu, Lei, Wan, Gong, and Zhou. "Heteroepitaxial Growth of High-Quality and Crack-Free AlN Film on Sapphire Substrate with Nanometer-Scale-Thick AlN Nucleation Layer for AlGaN-Based Deep Ultraviolet Light-Emitting Diodes." Nanomaterials 9, no. 11 (2019): 1634. http://dx.doi.org/10.3390/nano9111634.

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High-quality and crack-free aluminum nitride (AlN) film on sapphire substrate is the foundation for high-efficiency aluminum gallium nitride (AlGaN)-based deep ultraviolet light-emitting diodes (DUV LEDs). We reported the growth of high-quality and crack-free AlN film on sapphire substrate with a nanometer-scale-thick AlN nucleation layer (NL). Three kinds of nanometer-scale-thick AlN NLs, including in situ low-temperature AlN (LT-AlN) NL, oxygen-undoped ex situ sputtered AlN NL, and oxygen-doped ex situ sputtered AlN NL, were prepared for epitaxial growth of AlN films on sapphire substrates. The influence of nanoscale AlN NL thickness on the optical transmittance, strain state, surface morphology, and threading dislocation (TD) density of the grown AlN film on sapphire substrate were carefully investigated. The average optical transmittance of AlN film on sapphire substrate with oxygen-doped sputtered AlN NL was higher than that of AlN films on sapphire substrates with LT-AlN NL and oxygen-undoped sputtered AlN NL in the 200–270 nm wavelength region. However, the AlN film on sapphire substrate with oxygen-undoped sputtered AlN NL had the lowest TD density among AlN films on sapphire substrates. The AlN film on sapphire substrate with the optimum thickness of sputtered AlN NL showed weak tensile stress, a crack-free surface, and low TD density. Furthermore, a 270-nm AlGaN-based DUV LED was grown on the high-quality and crack-free AlN film. We believe that our results offer a promising and practical route for obtaining high-quality and crack-free AlN film for DUV LED.

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Zhao, Fengyi, Wei Jia, Hailiang Dong, et al. "Simulation and theoretical study of AlGaN-based deep-ultraviolet light-emitting diodes with a stepped electron barrier layer." AIP Advances 12, no. 12 (2022): 125003. http://dx.doi.org/10.1063/5.0127070.

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Owing to the COVID-19 outbreak, sterilization of deep-ultraviolet light-emitting diodes (DUV LEDs) has attracted increasing attention. Effectively improving the radiative recombination efficiency and mitigating the efficiency degradation, mainly caused by electron leakage and nonradiative recombination, have also emerged as two of the main issues to be addressed. In this study, a DUV LED epitaxial structure with a novel electron-blocking layer (EBL) is proposed. The DUV LED with a luminescence wavelength of ∼297 nm was formed by the stepwise variation of the Al component. Through the simulation and analysis of its performance parameters, we found that, compared to the conventional EBL structure, this new EBL structure not only reduces the electron leakage to the p-region effectively but also increases the hole injection into the active region, resulting in an increase in carrier concentration in the active region, a two-to-three-fold increase in the radiative recombination rate, and a 58% increase in the internal quantum efficiency, thus alleviating the efficiency droop and achieving a more efficient operation at high current densities.

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Shao, Hua, Jiamang Che, Chunshuang Chu, et al. "On the impact of a metal–insulator–semiconductor structured n-electrode for AlGaN-based DUV LEDs." Applied Optics 60, no. 36 (2021): 11222. http://dx.doi.org/10.1364/ao.446613.

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Yamada, Kiho, Yosuke Nagasawa, Shoko Nagai, et al. "Study on the Main-Chain Structure of Amorphous Fluorine Resins for Encapsulating AlGaN-Based DUV-LEDs." physica status solidi (a) 215, no. 10 (2018): 1700525. http://dx.doi.org/10.1002/pssa.201700525.

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Gaska, Ignas, Olga Bilenko, Saulius Smetona, Yuri Bilenko, Remis Gaska, and Michael Shur. "Deep UV LEDs for Public Health Applications." International Journal of High Speed Electronics and Systems 23, no. 03n04 (2014): 1450018. http://dx.doi.org/10.1142/s0129156414500189.

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In 2011, According to the World Health Organization, roughly 768 million people did not use any improved sources for drinking water while 185 million people relied on only regular surface water in order to meet their drinking water needs. The number of people living in slums with no clean water supply is expected to double by 2030 to 2 billion. Each year in U.S. hospitals there are an estimated 1.7 million healthcare acquired infections (HAI) resulting in approximately 99,000 deaths (2007 data). Deep Ultraviolet Light Emitting Diodes (DUV LEDs) technology can help solve these and a variety of other problems related to public health and wellbeing. In contrast to more conventional UV sources, such as mercury lamps, DUV LEDs do not require any warm up time, are toxic chemical free, and possess the capability to be molded into compact systems. The DUV LED diodes fabricated by SET, Inc. are based on III-Nitride Semiconductors ( AlGaN ). These devices are capable of providing spectral power distribution with the peak emission wavelengths from 227 nm to 340 nm. A novel compact low flow water purification unit using DUV LEDs demonstrated a 4.15 LOG reduction of viral MS2 bacteriophage and > 6 LOG (99.9999%) reduction of E.coli at 100mL/min flow and 40mW of optical output power. At higher optical output powers, the LOG reduction begins to saturate and taper off. The water disinfection unit incorporated 20 TO-39 packages and was controlled by a single custom power supply. Arrangement of the LEDs insured minimal to no shadowing of influent water. The germicidal efficacy of the system was further enhanced by photon recycling using UV-reflecting chamber walls and multiple passes through exposed water stream. The water disinfection units are geared towards affordable and durable Point-of-Use (POU) drinking water systems. Current modifications are being made in order to further increase the efficacy of the water disinfection units at higher flow rates and lower power requirements. DUV LED technology was also used to design efficient hard surface microbial disinfection systems. Many microbes have become more resistant to everyday chemical disinfectants. Higher dose and more concentrated chemical solutions are needed to the point that they themselves become toxic for humans. Initial testing has produced visual evidence of microbial inactivation on hard surfaces contaminated with E.coli. Testing involved a single SETi TO-39 package with a wavelength of approximately 275nm. A higher than the 2 LOG reduction at approximately 1 mW optical output power was achieved. Based on these results, a 2nd generation system was designed for portable DUV LED cell phone disinfection containing few separate LED chips at 270-275 nm. Initial testing revealed an almost 2 LOG (99%) reduction of E.coli after 30 minutes of exposure at low microbial influent levels.

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Zhang, Ji, Le Chang, Yuxin Zheng, et al. "Integrating remote reflector and air cavity into inclined sidewalls to enhance the light extraction efficiency for AlGaN-based DUV LEDs." Optics Express 28, no. 11 (2020): 17035. http://dx.doi.org/10.1364/oe.393166.

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Maeda, Noritoshi, Masafumi Jo, and Hideki Hirayama. "Improving the Light-Extraction Efficiency of AlGaN DUV-LEDs by Using a Superlattice Hole Spreading Layer and an Al Reflector." physica status solidi (a) 215, no. 8 (2018): 1700436. http://dx.doi.org/10.1002/pssa.201700436.

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Tian, Yucheng, Hui Wang, Xiangning Kang, et al. "The mesa design guidance based on the effective range of the mesa sidewall reflector towards high-efficiency AlGaN-based DUV LEDs." Micro and Nanostructures 186 (February 2024): 207737. http://dx.doi.org/10.1016/j.micrna.2023.207737.

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Chu, Chunshuang, Danyang Zhang, Hua Shao, et al. "Reducing the polarization mismatch between the last quantum barrier and p-EBL to enhance the carrier injection for AlGaN-based DUV LEDs." Optical Materials Express 11, no. 6 (2021): 1713. http://dx.doi.org/10.1364/ome.424281.

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Yin, Yue, Fang Ren, Yunyu Wang, et al. "Direct van der Waals Epitaxy of Crack-Free AlN Thin Film on Epitaxial WS2." Materials 11, no. 12 (2018): 2464. http://dx.doi.org/10.3390/ma11122464.

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Van der Waals epitaxy (vdWE) has drawn continuous attention, as it is unlimited by lattice-mismatch between epitaxial layers and substrates. Previous reports on the vdWE of III-nitride thin film were mainly based on two-dimensional (2D) materials by plasma pretreatment or pre-doping of other hexagonal materials. However, it is still a huge challenge for single-crystalline thin film on 2D materials without any other extra treatment or interlayer. Here, we grew high-quality single-crystalline AlN thin film on sapphire substrate with an intrinsic WS2 overlayer (WS2/sapphire) by metal-organic chemical vapor deposition, which had surface roughness and defect density similar to that grown on conventional sapphire substrates. Moreover, an AlGaN-based deep ultraviolet light emitting diode structure on WS2/sapphire was demonstrated. The electroluminescence (EL) performance exhibited strong emissions with a single peak at 283 nm. The wavelength of the single peak only showed a faint peak-position shift with increasing current to 80 mA, which further indicated the high quality and low stress of the AlN thin film. This work provides a promising solution for further deep-ultraviolet (DUV) light emitting electrodes (LEDs) development on 2D materials, as well as other unconventional substrates.

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Zhang, Gai, Hua Shao, Muyao Zhang, et al. "Enhancing the light extraction efficiency for AlGaN-based DUV LEDs with a laterally over-etched p-GaN layer at the top of truncated cones." Optics Express 29, no. 19 (2021): 30532. http://dx.doi.org/10.1364/oe.435302.

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Li, Liang, Mei Cui, Hua Shao, et al. "Demonstration of ohmic contact using ${{\rm MoO}_{\rm x}}/{\rm Al}$MoOx/Al on p-GaN and the proposal of a reflective electrode for AlGaN-based DUV-LEDs." Optics Letters 45, no. 8 (2020): 2427. http://dx.doi.org/10.1364/ol.387275.

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Sampath, Anand V., Yoajia Chen, Q. Zhou, et al. "AlGaN/SiC Heterojunction Ultraviolet Photodiodes." Materials Science Forum 858 (May 2016): 1206–9. http://dx.doi.org/10.4028/www.scientific.net/msf.858.1206.

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We report on improvement in the deep ultraviolet (DUV) photoresponse of SiC based detectors through the development of n- AlxGa1-xN / i-p SiC heterojunction photodiodes. Fabricated photodiodes have high external quantum efficiency (EQE), greater than 60%, over a wide spectral range from 215-255 nm that is ~10x enhancement in performance over comparable homogenous SiC photodiodes at the shortest wavelength. This is attributed to photogeneration of carriers within the SiC depletion region by DUV illumination of the diode through the n- AlxGa1-xN “window”, as compared to a typical homogenous SiC n-i-p structure where the carriers are photogenerated in the n-type neutral region, resulting in more efficient collection of holes through drift

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Zhao, Yiming, Zijie Wang, and Xiaolin Feng. "Research Progress of AlGaN Ultraviolet Light-Emitting Diodes." E3S Web of Conferences 560 (2024): 01006. http://dx.doi.org/10.1051/e3sconf/202456001006.

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The research progress of AlGaN ultraviolet light-emitting diodes (UV LEDs) is explored in this paper. Firstly, the significance and application areas of AlGaN UV LEDs are introduced, emphasizing their wide-ranging applications in fields such as disinfection, medical devices, and sensors. Subsequently, an overview of the material science and manufacturing processes used in the production of AlGaN UV LEDs is provided, including crystal growth techniques and fabrication processes. Next, the design, structure, and operating principles of different types of AlGaN UV LEDs are described, with a focus on the devices optical performance, electrical characteristics, and thermal management effects. Finally, the latest research findings are summarized, and the challenges and future development directions facing current technology are discussed. This paper aims to provide readers with a comprehensive understanding of the research field of AlGaN UV LEDs and serve as a reference for future research and applications.

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Gao, Jianghong, Qiushuang Chen, Hongyu Liu, et al. "Degradation behaviors of deep ultraviolet LEDs: The role of polarization induced doping in p-AlGaN layer." Journal of Physics D: Applied Physics, June 19, 2025. https://doi.org/10.1088/1361-6463/ade600.

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Abstract Polarization-induced doping in p-AlGaN consisting composition gradient AlGaN has been widely utilized in AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) to enhance hole injection. Yet the presence of polarization doping on the degradation behaviors of DUV-LED still remains largely unexplored. In this work, time-dependent electrical, optical properties and degradation mechanisms of 273 nm AlGaN-based DUV-LEDs with and without polarization doping were comprehensively investigated. Compared with DUV-LED incorporating bulk p-AlGaN, polarization-doped DUV-LED reveals lower leakage current, higher output power and longer lifetime due to its unique compositionally graded structure. The external quantum efficiency (EQE) versus current density (J) curves before and after electrical stress were fitted by the ABC + f(n) model. Four-times enhancement in Auger recombination coefficient was obtained for conventional LED after aging, while 185% increased non-radiative recombination coefficient was identified in polarization doped DUV-LEDs, suggesting different roles played between bulk and polarization-doped p-AlGaN during device aging process.

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Liu, Xu, Zhenxing Lv, Zhefu Liao, et al. "Highly efficient AlGaN-based deep-ultraviolet light-emitting diodes: from bandgap engineering to device craft." Microsystems & Nanoengineering 10, no. 1 (2024). http://dx.doi.org/10.1038/s41378-024-00737-x.

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AbstractAlGaN-based light-emitting diodes (LEDs) operating in the deep-ultraviolet (DUV) spectral range (210–280 nm) have demonstrated potential applications in physical sterilization. However, the poor external quantum efficiency (EQE) hinders further advances in the emission performance of AlGaN-based DUV LEDs. Here, we demonstrate the performance of 270-nm AlGaN-based DUV LEDs beyond the state-of-the-art by exploiting the innovative combination of bandgap engineering and device craft. By adopting tailored multiple quantum wells (MQWs), a reflective Al reflector, a low-optical-loss tunneling junction (TJ) and a dielectric SiO2 insertion structure (IS-SiO2), outstanding light output powers (LOPs) of 140.1 mW are achieved in our DUV LEDs at 850 mA. The EQEs of our DUV LEDs are 4.5 times greater than those of their conventional counterparts. This comprehensive approach overcomes the major difficulties commonly faced in the pursuit of high-performance AlGaN-based DUV LEDs, such as strong quantum-confined Stark effect (QCSE), severe optical absorption in the p-electrode/ohmic contact layer and poor transverse magnetic (TM)-polarized light extraction. Furthermore, the on-wafer electroluminescence characterization validated the scalability of our DUV LEDs to larger production scales. Our work is promising for the development of highly efficient AlGaN-based DUV LEDs.

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Feng Liya, Lu Huimin, Zhu Yifan, Chen Yiyong, Yu Tongjun, and Wang Jianping. "Intelligent Optimization Design of Electron Barrier Layer for AlGaN-based Deep-Ultraviolet Light-Emitting Diodes." Acta Physica Sinica, 2023, 0. http://dx.doi.org/10.7498/aps.72.20222004.

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AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) are widely used in sterilization, sensing, water purification, medical treatment, non-line of sight (NLOS) communication and many other fields. Especially it has been reported that the global novel coronavirus (COVID-19) can be effectively inactivated by the DUV light with a wavelength below 280 nm (UVC) within a few seconds, which has also attracted great attention. However, the external quantum efficiency (EQE) of UVC LEDs is still at a low level, generally not more than 10%. As an important component of EQE, internal quantum efficiency (IQE) plays a crucial role in realizing high-performance DUV-LEDs. In order to improve the IQE of AlGaN-based DUV-LEDs, this work adopts an electron blocking layer (EBL) structure based on InAlGaN/AlGaN superlattice. The results show that the superlattice EBL structure can effectively improve the IQE compared with the traditional single-layer and double-layer EBL structures for the DUV-LEDs. On this basis, it is proposed optimization method based on JAYA intelligent algorithm for LED structure design in this work. Using the proposed design method, the InAlGaN/AlGaN superlattice EBL structure is further optimized to maximize the LEDs’ IQE. It is demonstrated that the optimized superlattice EBL structure is beneficial to not only the suppression of electron leakage but also the improvement of hole injection, leading to the increase of carrier recombination in the active region. As a result, the IQE of the DUV-LED at 200 mA injection current is 41.2% higher than that of the single-layer EBL structure. In addition, the optimized structure reduces IQE droop at high current from 25% to 4%. The optimization method based on intelligent algorithm can break through the limitations of the current LED structure design and provide a new method to improve the efficiency of AlGaN-based DUV-LEDs.

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Liao, Zhefu, Zhenxing Lv, Bin Tang, et al. "Redirection‐Manipulated Honeycomb Inclined Reflection System Enables Highly Efficient AlGaN‐Based Deep‐Ultraviolet Light‐Emitting Diodes." Laser & Photonics Reviews, February 12, 2025. https://doi.org/10.1002/lpor.202401698.

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AbstractAlGaN‐based deep‐ultraviolet light‐emitting diodes (DUV LEDs) are considered promising and efficient solid‐state DUV light sources. However, extracting photons directly from high‐Al‐content AlGaN multiple quantum wells active region where the ratio of transverse magnetic (TM)/transverse electric (TE) polarization emission increases has long been challenging due to the total internal reflection phenomenon and re‐absorption effect, leading to the low efficiency of DUV LEDs. Herein, a redirection‐manipulated honeycomb inclined reflection system (HIRS) is demonstrated aimed at efficiently extracting TM‐ and TE‐polarized light from DUV LEDs, and systematically analyze the influence of the HIRS configurations on the resulting redirection effect. Crucially, the investigation reveals the effective range of the HIRS redirection effect, prompting the proposal of a pixelation strategy applicable to generalized AlGaN‐based DUV LEDs. This strategy is validated through the experimental fabrication of pixelated DUV LEDs integrated with HIRS. Compared to their non‐pixelated, non‐HIRS counterparts, these pixelated DUV LEDs integrated with HIRS achieve a light output power enhancement factor of up to 1.95, surpassing all previously reported pixelated DUV LEDs. Furthermore, the double‐side‐coated sapphire is introduced as a package plate to improve reliability and optical performance and develop a miniaturized sterilization module for effective water purification. This work not only provides guidance for high‐power AlGaN‐based DUV LEDs design and manufacture but also advances the development of efficient solutions for water purification.

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Li, Hongbo, Shunpeng Lu, Licai Zhu, et al. "Efficiency boosting of 236 nm AlGaN-based micro-LEDs." Journal of Physics D: Applied Physics, August 20, 2024. http://dx.doi.org/10.1088/1361-6463/ad714b.

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Abstract In this study, 236 nm AlGaN-based deep ultraviolet (DUV) Micro-LEDs with different sized P-contact areas are designed and fabricated, and the sidewall is restored by wet chemical treatment method with KOH solution. The results reveal that proper KOH treatment could effectively remove plasma damaged materials and clearly show the formation of m-plane facets. Compared with untreated Micro-LEDs, the reverse leakage current of the treated Micro-LEDs under -10 V decreases by up to 91.7% and the specific contact resistivity reduces from 6.94 Ωcm2 to 0.07 Ωcm2. The underlying mechanism is that KOH treatment removes the sidewall defects which leads to surface nonradiative recombination sites and surface leakage. Moreover, KOH treatment also removes contaminations on the P+-GaN surface and leads to lower specific contact resistivity. However, too long treatment also destructs the 20 nm P+-GaN layer, which results in higher voltage but less DUV light absorption. As a result, peak light output power density increases from 2.12 W/cm2 to 4.01 W/cm2, representing an 89.2% increase. The efficiency enhancement of Micro-LEDs is anticipated to facilitate the development of DUV Micro-LEDs in maskless lithography and high-capacity DUV non-line of sight communication.

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Fang, Xuzhou, Jiaming Wang, Fujun Xu, et al. "Elimination of spiral hillocks in AlGaN grown on high-temperature annealed AlN templates by adopting an AlN/AlGaN stress modulation multilayer." Applied Physics Letters 124, no. 6 (2024). http://dx.doi.org/10.1063/5.0184353.

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The formation of spiral hillocks during AlGaN growth is investigated by modulating the residual strain in the underlying AlN templates. It is demonstrated that the high-density hillocks are directly related to the compressive stress, in particular for AlGaN on high-temperature annealed (HTA) AlN. AlN/AlGaN stress modulation multilayer is then introduced and optimized before AlGaN growth, which is revealed to be helpful to release the compressive stress in AlGaN as well as to suppress the hillocks. Eventually, the hillocks in AlGaN/HTA-AlN are eliminated, leading to a great improvement of yield for deep-ultraviolet light-emitting diode (DUV-LED) wafers. This work will definitely promote further industrial development and application of DUV-LEDs.

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Chen, Zhenyu, Shuang Zhang, Yongming Zhao, et al. "Enhancement of Light Extraction Efficiency in AlGaN‐Based Deep Ultraviolet Light‐Emitting Diodes Using Cooperative Scattering Structures on the n‐AlGaN Layer." Laser & Photonics Reviews, January 24, 2025. https://doi.org/10.1002/lpor.202401926.

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AbstractThe efficiency of AlGaN based deep ultraviolet light‐emitting diode (DUV LEDs) are mainly hindered by the light extraction issue. In this work, an innovative cooperative scattering structure is introduced that combines a nanopore configuration with an aluminum (Al) nanoparticle array on the n‐AlGaN layer of the DUV LEDs. The integration of these two scattering arrays can enhance light extraction by mitigating total internal reflection at the device interface. The nanopores are formed on the n‐AlGaN surface by electrochemical etching and optimized by varying the etching voltage, while the Al particles are formed by thermal annealing. With the help of the cooperative scattering structure, the light output power (LOP) of the optimized DUV LEDs is significantly increased by 77.6% and a notable 2.2 times is achieved in its light extraction efficiency (LEE) enhancement factor. Moreover, Finite‐Difference Time‐Domain (FDTD) simulations have validated that the cooperative scattering structure considerably enhances the LEE for both Transverse Electric (TE) and Transverse Magnetic (TM) modes, respectively. This work paves the way to fabricate high efficiency DUV LEDs via novel scattering structure designs.

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