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Lu S, Jiang X, Wang Y, Huang K, Gao N, Cai D, Zhou Y, Yang CC, Kang J, Zhang R. Enhancing deep-UV emission at 234 nm by introducing a truncated pyramid AlN/GaN nanostructure with fine-tuned multiple facets. NANOSCALE 2022; 14:653-662. [PMID: 35018953 DOI: 10.1039/d1nr06188g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The external quantum efficiency of a high-Al content (>0.6) AlGaN deep-ultraviolet (DUV) light-emitting diode is typically below 1% in the sub-250 nm wavelength range. One of the main reasons for this low efficiency is the fundamental properties of high-Al content AlGaN comprising the transverse-magnetic (TM)-dominant emission and low light extraction due to the total internal reflection (TIR). This work demonstrates a truncated pyramid nanostructure with fine-tuned multiple facets in an (AlN)8/(GaN)2 digital alloy to achieve highly efficient DUV emission at 234 nm. By applying nanoimprint lithography, dry and wet etching, a hexagonal truncated pyramid nanohole structure is fabricated featuring multiple crystal facets of (0001), (10-13), and (20-21) planes. These fine-tuned multiple facets act as reflecting mirrors that can effectively modulate the light propagation and extraction patterns to overcome the TIR via multiple reflections and enhanced scattering. Consequently, significant light extraction enhancements of 5.6 times and 1.1 times for TM and transverse-electric emissions are achieved in the truncated pyramid nanohole structure, respectively. The total luminous intensity of this unique nanostructure is greatly increased by 191% compared to that of a conventional planar structure. The truncated pyramid AlN/GaN nanostructure with fine-tuned multiple facets used in this work provides a promising approach for realizing highly efficient sub-250 nm DUV light-emitting devices.
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Affiliation(s)
- Shiqiang Lu
- Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, Department of Physics, Xiamen University, Xiamen 361005, China.
| | - Xinjun Jiang
- Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Yaozeng Wang
- Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Kai Huang
- Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, Department of Physics, Xiamen University, Xiamen 361005, China.
| | - Na Gao
- Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, Department of Physics, Xiamen University, Xiamen 361005, China.
| | - Duanjun Cai
- Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, Department of Physics, Xiamen University, Xiamen 361005, China.
| | - Yinghui Zhou
- Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, Department of Physics, Xiamen University, Xiamen 361005, China.
| | - C C Yang
- Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Junyong Kang
- Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, Department of Physics, Xiamen University, Xiamen 361005, China.
| | - Rong Zhang
- Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, Department of Physics, Xiamen University, Xiamen 361005, China.
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Li J, Gao N, Cai D, Lin W, Huang K, Li S, Kang J. Multiple fields manipulation on nitride material structures in ultraviolet light-emitting diodes. LIGHT, SCIENCE & APPLICATIONS 2021; 10:129. [PMID: 34150202 PMCID: PMC8206881 DOI: 10.1038/s41377-021-00563-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 04/25/2021] [Accepted: 05/24/2021] [Indexed: 05/22/2023]
Abstract
As demonstrated during the COVID-19 pandemic, advanced deep ultraviolet (DUV) light sources (200-280 nm), such as AlGaN-based light-emitting diodes (LEDs) show excellence in preventing virus transmission, which further reveals their wide applications from biological, environmental, industrial to medical. However, the relatively low external quantum efficiencies (mostly lower than 10%) strongly restrict their wider or even potential applications, which have been known related to the intrinsic properties of high Al-content AlGaN semiconductor materials and especially their quantum structures. Here, we review recent progress in the development of novel concepts and techniques in AlGaN-based LEDs and summarize the multiple physical fields as a toolkit for effectively controlling and tailoring the crucial properties of nitride quantum structures. In addition, we describe the key challenges for further increasing the efficiency of DUV LEDs and provide an outlook for future developments.
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Affiliation(s)
- Jinchai Li
- Engineering Research Center of Micro-nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Key Laboratory of Semiconductor Materials and Applications, CI center for OSED, College of Physical Science and Technology, Xiamen University, 361005 Xiamen, China
| | - Na Gao
- Engineering Research Center of Micro-nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Key Laboratory of Semiconductor Materials and Applications, CI center for OSED, College of Physical Science and Technology, Xiamen University, 361005 Xiamen, China
| | - Duanjun Cai
- Engineering Research Center of Micro-nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Key Laboratory of Semiconductor Materials and Applications, CI center for OSED, College of Physical Science and Technology, Xiamen University, 361005 Xiamen, China
| | - Wei Lin
- Engineering Research Center of Micro-nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Key Laboratory of Semiconductor Materials and Applications, CI center for OSED, College of Physical Science and Technology, Xiamen University, 361005 Xiamen, China
| | - Kai Huang
- Engineering Research Center of Micro-nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Key Laboratory of Semiconductor Materials and Applications, CI center for OSED, College of Physical Science and Technology, Xiamen University, 361005 Xiamen, China
| | - Shuping Li
- Engineering Research Center of Micro-nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Key Laboratory of Semiconductor Materials and Applications, CI center for OSED, College of Physical Science and Technology, Xiamen University, 361005 Xiamen, China
| | - Junyong Kang
- Engineering Research Center of Micro-nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Key Laboratory of Semiconductor Materials and Applications, CI center for OSED, College of Physical Science and Technology, Xiamen University, 361005 Xiamen, China
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Chen L, Lin W, Wang H, Li J, Kang J. Reversing abnormal hole localization in high-Al-content AlGaN quantum well to enhance deep ultraviolet emission by regulating the orbital state coupling. LIGHT, SCIENCE & APPLICATIONS 2020; 9:104. [PMID: 32577220 PMCID: PMC7299972 DOI: 10.1038/s41377-020-00342-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 05/29/2020] [Accepted: 06/04/2020] [Indexed: 05/29/2023]
Abstract
AlGaN has attracted considerable interest for ultraviolet (UV) applications. With the development of UV optoelectronic devices, abnormal carrier confinement behaviour has been observed for c-plane-oriented AlGaN quantum wells (QWs) with high Al content. Because of the dispersive crystal field split-off hole band (CH band) composed of p z orbitals, the abnormal confinement becomes the limiting factor for efficient UV light emission. This observation differs from the widely accepted concept that confinement of carriers at the lowest quantum level is more pronounced than that at higher quantum levels, which has been an established conclusion for conventional continuous potential wells. In particular, orientational p z orbitals are sensitive to the confinement direction in line with the conducting direction, which affects the orbital intercoupling. In this work, models of Al0.75Ga0.25N/AlN QWs constructed with variable lattice orientations were used to investigate the orbital intercoupling among atoms between the well and barrier regions. Orbital engineering of QWs was implemented by changing the orbital state confinement, with the well plane inclined from 0° to 90° at a step of 30° (referred to the c plane). The barrier potential and transition rate at the band edge were enhanced through this orbital engineering. The concept of orbital engineering was also demonstrated through the construction of inclined QW planes on semi- and nonpolar planes implemented in microrods with pyramid-shaped tops. The higher emission intensity from the QWs on the nonpolar plane compared with those on the polar plane was confirmed via localized cathodoluminescence (CL) maps.
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Affiliation(s)
- Li Chen
- Engineering Research Center of Micro-nano Optoelectronic Materials and Devices, Ministry of Education; Fujian Provincial Key Laboratory of Semiconductor Materials and Applications; Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices; Department of Physics, Xiamen University, 361005 Xiamen, China
- Present Address: Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, 315201 Ningbo, Zhejiang China
| | - Wei Lin
- Engineering Research Center of Micro-nano Optoelectronic Materials and Devices, Ministry of Education; Fujian Provincial Key Laboratory of Semiconductor Materials and Applications; Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices; Department of Physics, Xiamen University, 361005 Xiamen, China
| | - Huiqiong Wang
- Engineering Research Center of Micro-nano Optoelectronic Materials and Devices, Ministry of Education; Fujian Provincial Key Laboratory of Semiconductor Materials and Applications; Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices; Department of Physics, Xiamen University, 361005 Xiamen, China
| | - Jinchai Li
- Engineering Research Center of Micro-nano Optoelectronic Materials and Devices, Ministry of Education; Fujian Provincial Key Laboratory of Semiconductor Materials and Applications; Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices; Department of Physics, Xiamen University, 361005 Xiamen, China
| | - Junyong Kang
- Engineering Research Center of Micro-nano Optoelectronic Materials and Devices, Ministry of Education; Fujian Provincial Key Laboratory of Semiconductor Materials and Applications; Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices; Department of Physics, Xiamen University, 361005 Xiamen, China
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Noor-A-Alam M, Z Olszewski O, Nolan M. Ferroelectricity and Large Piezoelectric Response of AlN/ScN Superlattice. ACS APPLIED MATERIALS & INTERFACES 2019; 11:20482-20490. [PMID: 31074260 DOI: 10.1021/acsami.8b22602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Based on density functional theory, we investigate the ferroelectric and piezoelectric properties of the AlN/ScN superlattice, consisting of ScN and AlN buckled monolayers alternating along the crystallographic c-direction. We find that the polar wurtzite (w-ScAlN) structure is mechanically and dynamically stable and is more stable than the nonpolar hexagonal flat configuration. We show that ferroelectric polarization switching can be possible for an epitaxially tensile-strained superlattice. Because of the elastic constant C33 softening, together with an increase in e33, the piezoelectric coefficient d33 of the superlattice is doubled compared to that of pure w-AlN. The combined enhancement of Born effective charges ( Z33) and sensitivity of the atomic coordinates to the external strain (∂u3∂η3) is the origin of the large piezoelectric constant e33. Moreover, we show that the epitaxial biaxial tensile strain significantly enhances the piezo-response, so that d33 becomes 7 times larger than that of w-AlN at 4% strain. The tensile strain results in a huge enhancement in e33 by increasing Z33 and ∂u3∂η3 , which boost the piezoelectric.
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Affiliation(s)
- Mohammad Noor-A-Alam
- Tyndall National Institute, University College Cork , Lee Maltings, Dyke Parade , Cork T12 R5CP , Ireland
| | - Oskar Z Olszewski
- Tyndall National Institute, University College Cork , Lee Maltings, Dyke Parade , Cork T12 R5CP , Ireland
| | - Michael Nolan
- Tyndall National Institute, University College Cork , Lee Maltings, Dyke Parade , Cork T12 R5CP , Ireland
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Xue J, Zhu Z, Xu X, Gu Y, Wang S, Xu L, Zou Y, Song J, Zeng H, Chen Q. Narrowband Perovskite Photodetector-Based Image Array for Potential Application in Artificial Vision. NANO LETTERS 2018; 18:7628-7634. [PMID: 30457343 DOI: 10.1021/acs.nanolett.8b03209] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Image sensor arrays are widely used in digital cameras, smartphones, and biorobots. However, most commercial image arrays rely on the dichroic prisms or a set of interference filters to distinguish characteristic color spectrum, which significantly increases the cost and fabrication processing complexity. In this work, an ultranarrow response photodetector with full-width at half-maximum being ∼12 nm and specific detectivity over 1011 Jones at 545 nm are successfully achieved in CsPbBr3 polycrystalline films using freeze-drying casting method to adjust the surface-charge recombination. To our best knowledge, this is the narrowest spectrum response for perovskite photodetectors in the visible light waveband. More importantly, a series of narrowband photodetectors are developed to enhance diverse selectivity for target signals covering from blue light to red light via bandgap tuning in CsPbX3 by tailoring the halide component. Finally, an integrated sensing array with CsPbX3 (X = Cl, Br, I) narrowband photodetectors acting as color recognition cones is constructed, which presents clear color and shape recognition paving the way for commercialization of perovskite photodetector in artificial vision.
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Zheng J, Li J, Zhong Z, Lin W, Chen L, Li K, Wang X, Chou C, Li S, Kang J. Effect of electrical injection-induced stress on interband transitions in high Al content AlGaN MQWs. RSC Adv 2017. [DOI: 10.1039/c7ra10440e] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The light extraction from AlGaN deep ultraviolet light-emitting diodes (UV LEDs) is known to be limited by the fundamental valence band crossover issue.
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Affiliation(s)
- Jinjian Zheng
- Department of Physics
- Fujian Provincial Key Laboratory of Semiconductor Materials and Applications
- Xiamen University
- Xiamen
- P. R. China
| | - Jinchai Li
- Department of Physics
- Fujian Provincial Key Laboratory of Semiconductor Materials and Applications
- Xiamen University
- Xiamen
- P. R. China
| | - Zhibai Zhong
- Department of Physics
- Fujian Provincial Key Laboratory of Semiconductor Materials and Applications
- Xiamen University
- Xiamen
- P. R. China
| | - Wei Lin
- Department of Physics
- Fujian Provincial Key Laboratory of Semiconductor Materials and Applications
- Xiamen University
- Xiamen
- P. R. China
| | - Li Chen
- Department of Physics
- Fujian Provincial Key Laboratory of Semiconductor Materials and Applications
- Xiamen University
- Xiamen
- P. R. China
| | - Kongyi Li
- Department of Physics
- Fujian Provincial Key Laboratory of Semiconductor Materials and Applications
- Xiamen University
- Xiamen
- P. R. China
| | - Xinghe Wang
- San'an Optoelectronics Co., Ltd
- Xiamen
- P. R. China
| | - Chilun Chou
- San'an Optoelectronics Co., Ltd
- Xiamen
- P. R. China
| | - Shuiqing Li
- San'an Optoelectronics Co., Ltd
- Xiamen
- P. R. China
| | - Junyong Kang
- Department of Physics
- Fujian Provincial Key Laboratory of Semiconductor Materials and Applications
- Xiamen University
- Xiamen
- P. R. China
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Cho SW, Jeong M, Kim JH, Kwon YH, Kim H, Lee JY, Cho HK. A combinatorial approach to solution-processed InGaO3(ZnO)m superlattice films: growth mechanisms and their thermoelectric properties. CrystEngComm 2016. [DOI: 10.1039/c5ce01764e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The strong single-phase InGaO3(ZnO)m films with superlattice structures showed superior thermoelectric power factors. Their microstructural growth evolution was investigated using transmission electron microscopy in detail.
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Affiliation(s)
- Sung Woon Cho
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon, Republic of Korea
| | - Myoungho Jeong
- Center for Nanomaterials and Chemical Reactions
- Institute for Basic Science (IBS)
- Daejeon, Republic of Korea
- Department of Materials Science and Engineering
- Korea Advanced Institute of Science and Technology (KAIST)
| | - Jun Hyeon Kim
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon, Republic of Korea
| | - Yong Hun Kwon
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon, Republic of Korea
| | - Hyoungsub Kim
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon, Republic of Korea
| | - Jeong Yong Lee
- Center for Nanomaterials and Chemical Reactions
- Institute for Basic Science (IBS)
- Daejeon, Republic of Korea
- Department of Materials Science and Engineering
- Korea Advanced Institute of Science and Technology (KAIST)
| | - Hyung Koun Cho
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon, Republic of Korea
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Direct Observation of the Biaxial Stress Effect on Efficiency Droop in GaN-based Light-emitting Diode under Electrical Injection. Sci Rep 2015; 5:17227. [PMID: 26634816 PMCID: PMC4669452 DOI: 10.1038/srep17227] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 10/27/2015] [Indexed: 11/08/2022] Open
Abstract
Light-emitting diode (LED) efficiency has attracted considerable interest because of the extended use of solid-state lighting. Owing to lack of direct measurement, identification of the reasons for efficiency droop has been restricted. A direct measurement technique is developed in this work for characterization of biaxial stress in GaN-based blue LEDs under electrical injection. The Raman shift of the GaN E2 mode evidently decreases by 4.4 cm−1 as the driving current on GaN-based LEDs increases to 700 mA. Biaxial compressive stress is released initially and biaxial tensile stress builds up as the current increases with respect to the value of stress-free GaN. First-principles calculations reveal that electron accumulation is responsible for the stress variation in InxGa1−xN/GaN quantum wells, and then reduces the transition probability among quantum levels. This behavior is consistent with the measured current-dependent external quantum efficiency. The rule of biaxial stress-dependent efficiency is further validated by controlling the biaxial stress of GaN-based LEDs with different sapphire substrate thicknesses. This work provides a method for direct observation of the biaxial stress effect on efficiency droop in LEDs under electrical injection.
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