Article
Chemistry, Multidisciplinary
Farzan Shabani, Hamed Dehghanpour Baruj, Iklim Yurdakul, Savas Delikanli, Negar Gheshlaghi, Furkan Isik, Baiquan Liu, Yemliha Altintas, Betul Canimkurbey, Hilmi Volkan Demir
Summary: A new synthetic pathway is proposed for extending the emission wavelength of quasi-2D colloidal quantum wells into the deep-red region using multiple techniques. By developing a new method to obtain thick and passivated NPLs as seeds, and applying a final hot injection shell coating, thick NPLs with superior optical properties including high photoluminescence quantum yield of 88% are achieved. The deep-red LED device fabricated with these NPLs exhibits a high external quantum efficiency of 6.8% at 701 nm.
Article
Chemistry, Multidisciplinary
Marta Sawicka, Julita Smalc-Koziorowska, Marcin Krysko, Natalia Fiuczek, Pawel Wolny, Anna Feduniewicz-Zmuda, Krzesimir Nowakowski-Szkudlarek, Henryk Turski, Czeslaw Skierbiszewski
Summary: The study reports the indium incorporation efficiency and structural quality of nonpolar and semipolar InAIN layers grown by plasma-assisted molecular beam epitaxy. The indium content is found to depend on surface orientation, leading to different incorporation efficiencies for the different orientations. Additionally, one-dimensional strain relaxation is observed for the m-plane InAIN layer, while the semipolar and c-plane InAIN layers are strained to GaN.
CRYSTAL GROWTH & DESIGN
(2021)
Article
Chemistry, Multidisciplinary
Mingyuan Xie, Jie Guo, Xiaoyu Zhang, Chenghao Bi, Lin Zhang, Zema Chu, Weitao Zheng, Jingbi You, Jianjun Tian
Summary: This study presents a solution to achieve high-efficiency pure-red perovskite light-emitting diodes (PeLEDs) by stabilizing the structure of quantum dots and reducing adverse effects. The use of composite ligands helped stabilize the strong-confined quantum dots and suppress Auger recombination in the devices. Additionally, adjustments in the valence band of the quantum dots improved charge injection balance in the PeLEDs.
Review
Crystallography
Panpan Li, Hongjian Li, Matthew S. Wong, Philip Chan, Yunxuan Yang, Haojun Zhang, Mike Iza, James S. Speck, Shuji Nakamura, Steven P. Denbaars
Summary: InGaN-based red micro-size light-emitting diodes (μLEDs) are highly attractive due to their less influenced external quantum efficiency (EQE) by size effect compared to common AlInGaP-based red μLEDs. Additionally, InGaN red μLEDs exhibit robust device performance even at high temperatures up to 400K. This review discusses the progress of InGaN red μLEDs and explores novel growth methods to relax the strain and increase the growth temperature of InGaN red quantum wells.
Article
Engineering, Environmental
Min Lu, Jie Guo, Siqi Sun, Po Lu, Xiaoyu Zhang, Zhifeng Shi, William W. Yu, Yu Zhang
Summary: By replacing oleic acid ligands with octylphosphonic acid in the synthesis of perovskite QDs, the performance of the QDs was successfully improved, leading to enhanced fluorescence quantum efficiency and solution stability, as well as increased electrical conductivity of QD films. This ultimately resulted in highly efficient red perovskite QD LEDs with significantly improved luminance compared to LEDs based on pristine CsPbI3 QDs.
CHEMICAL ENGINEERING JOURNAL
(2021)
Article
Physics, Applied
Soichiro Morikawa, Kohei Ueno, Atsushi Kobayashi, Hiroshi Fujioka
Summary: The heavily Si-doped GaN (2021) exhibits high electron mobility and works well as a uniform current spreading layer and a hole injection layer on InGaN (2021) LEDs through the tunneling junction (TJ).
APPLIED PHYSICS EXPRESS
(2021)
Article
Engineering, Electrical & Electronic
Qiang Su, Heng Zhang, Shuming Chen
Summary: By utilizing transparent QLED elements, individually addressable red/green/blue emissions can be achieved in tandem QLEDs, with the ability to connect QLED elements in series or in parallel to improve external quantum efficiency.
This new implementation strategy for tandem QLEDs shows promising applications in both display and lighting fields, with enhanced EQE.
NPJ FLEXIBLE ELECTRONICS
(2021)
Article
Materials Science, Multidisciplinary
Baisheng Zhu, Tian Wang, Zhi-Kuang Tan
Summary: This study reports a unique formation of quantum-confined perovskite through a one-step solution-casting process. The resulting thin films enable precise spectral tuning in pure-bromide and pure-iodide perovskite, giving high-purity blue and red luminescence, respectively.
JOURNAL OF MATERIALS CHEMISTRY C
(2022)
Article
Chemistry, Physical
Gencai Pan, Xue Bai, Xinyu Shen, Lei Wang, Yanli Mao, Xu Chen, Wen Xu, He Shao, Donglei Zhou, Biao Dong, Lin Xu, Junhua Hu, Hongwei Song
Summary: A direct synthetic method for CsPbI3 nanorods was developed using YCl3 promotion, resulting in high-efficiency red emitting CsPbI3 NCs with small aspect ratio and improved performance. The YCl3-promoted CsPbI3 NRs showed promising prospects in optoelectronic devices, exhibiting excellent luminescence and conductivity in LED applications.
Article
Optics
Aparna Das
Summary: LEDs based on group III-nitride semiconductors have traditionally used the polar plane, but semipolar and nonpolar orientations offer advantages such as reducing internal electric field and higher indium incorporation. Semipolar LEDs demonstrate important properties and have bright prospects for green/yellow LEDs and lasers. Comprehensive studies are needed to fully harness the advantages of semipolar orientations.
OPTICS AND SPECTROSCOPY
(2022)
Article
Physics, Applied
Arwa Saud Abbas, Ahmed Y. Alyamani, Shuji Nakamura, Steven P. Denbaars
Summary: A damage-free substrate removal technique using photoelectrochemical etching (PECE) was applied in semipolar (2021) flip-chip laser diode (FC-LD) structures by incorporating sacrificial layer In0.12Ga0.88N single quantum well (SL-SQW) types. While 40 nm type I required processing under low-temperature KOH for developing high-quality green active region devices, 10 nm type II exhibited a smooth n-type GaN surface with room-temperature KOH, promoting the applicability of the proposed technique. Temperature-dependent PECE of SL-SQW types is crucial for advanced FC-LDs.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2021)
Article
Materials Science, Multidisciplinary
Sourav Roy, S. M. Tasmeeh Ahsan, Ashraful Hossain Howlader, Diponkar Kundu, Shakil Mahmud Boby, Md. Rasidul Islam, Md. Shahrukh Adnan Khan, Shuvagoto Dhar, Md. Amzad Hossain
Summary: Semipolar InGaN-made green light-emitting diodes (LEDs) have attracted significant attention for their potential as replacements for polar (0001)-oriented LEDs due to reduced efficiency droop and green gap phenomenon. However, theoretical investigations comparing internal quantum efficiency, output power, and 3 dB bandwidth in non-c-plane-oriented InGaN green LEDs are lacking. This study examines the impact of strain-induced polarization field on major optical and electronic characteristics of In0.29Ga0.71N/GaN green LED along different crystal orientations using a modified ABC model. The results demonstrate that (1122)-oriented InGaN green LED exhibits superior performance in terms of internal quantum efficiency, droop ratio, light emission spectra, output power, and I-V profile.
MATERIALS TODAY COMMUNICATIONS
(2022)
Article
Chemistry, Multidisciplinary
Wing-Kei Kwok, Lok-Kwan Li, Shiu-Lun Lai, Ming-Yi Leung, Wai Kit Tang, Shun-Cheung Cheng, Man-Chung Tang, Wai-Lung Cheung, Chi-Chiu Ko, Mei-Yee Chan, Vivian Wing-Wah Yam
Summary: A new class of gold(III) complexes containing acridinyl moieties and tetradentate C<^>C<^>N<^>N ligand has been designed and synthesized, which exhibit high photoluminescence quantum yields in solid-state thin films. These complexes have been utilized to fabricate high-performance OLEDs with high external quantum efficiencies and satisfactory operational half-lifetime values. The TADF properties of the complexes have been substantiated by various experimental techniques.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Materials Science, Multidisciplinary
Gun-Woo Lee, Jae-Hyeok Oh, Sung-Nam Lee
Summary: This study demonstrates the achievement of full-color monolithic LEDs using hexagonal epitaxial lateral overgrowth and pulse modulation modes. By reducing crystal defects and controlling indium incorporation, the LEDs emit red, green, and blue light with the same intensity, leading to the development of high-performance multifunctional lighting sources.
ADVANCED OPTICAL MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Pan Yin, Ting Zhi, Tao Tao, Xiaoyan Liu
Summary: In this study, GaN-based blue micro-light-emitting diodes (mu-LEDs) with different structures were designed, and the effect of quantum well (QW) structure on modulation bandwidth was explored. It was found that trapezoidal QWs can enhance modulation bandwidth and improve carrier lifetime.
Article
Physics, Applied
Chung-Chi Chen, Ting-Chun Huang, Yu-Wei Lin, Yu-Ren Lin, Ping-Hsiu Wu, Ping-Wei Liou, Hao-Yu Hsieh, Yang-Yi Huang, Shaobo Yang, Yuh-Renn Wu, C. C. Yang
Summary: Polarization-induced p-type behavior is produced by growing a series of AlGaN samples with decreasing Al contents along the c-axis on GaN templates using molecular beam epitaxy. The dependence of hole mobility on the central Al content is studied, showing a monotonic decrease with two different slopes in the two Al-content ranges divided at around 40%. The relaxation of tensile strain observed at Al contents higher than 40% leads to an increase in overall polarization gradient and hole concentration.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Panpan Li, Hongjian Li, Yunxuan Yang, Haojun Zhang, Pavel Shapturenka, Matthew Wong, Cheyenne Lynsky, Mike Iza, Michael J. Gordon, James S. Speck, Shuji Nakamura, Steven P. DenBaars
Summary: In this work, ultra-small 5 x 5 mu m(2) amber mu LEDs with high EQE and low reverse current were demonstrated using InGaN materials, indicating their promising potential for AR and VR displays.
APPLIED PHYSICS LETTERS
(2022)
Article
Engineering, Electrical & Electronic
Pin-Fang Chen, Edward Chen, Yuh-Renn Wu
Summary: This study compared symmetric and asymmetric MoS2 nanosheet transistor structures, with results showing that the asymmetric structure achieved higher current density and better gate control. Optimization using Al2O3 as the dielectric and introducing AlOx material led to enhanced device performance and improved current density, demonstrating promising potential for low-power applications.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
Article
Materials Science, Multidisciplinary
Huan-Ting Shen, Yu-Chieh Chang, Yuh-Renn Wu
Summary: This study investigated the changes in polarization ratio induced by alloy fluctuations, showing that the TM polarization ratio increases with the Al composition in the buffer layer.
PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS
(2022)
Article
Multidisciplinary Sciences
Ray-Hua Horng, Chun-Xin Ye, Po-Wei Chen, Daisuke Iida, Kazuhiro Ohkawa, Yuh-Renn Wu, Dong-Sing Wuu
Summary: In this research, it is observed that the smaller the size of the InGaN red micro-LED, the more obvious the blue shift of the emission wavelength with increasing injection current. Smaller chip micro-LEDs exhibit similar output power density at the same injection current density.
SCIENTIFIC REPORTS
(2022)
Article
Physics, Applied
Cheng-Han Ho, James S. Speck, Claude Weisbuch, Yuh-Renn Wu
Summary: For nitride-based blue and green LEDs, the forward voltage is higher than expected, especially for green LEDs, due to polarization discontinuity at multiple quantum well and quantum barrier interfaces. V-shaped defects have been proposed as a key factor in reducing the forward voltage by enabling lateral carrier injection. In this study, the effects of random alloy fluctuations and V-defect density on carrier transport in the whole LED are modeled, revealing that V-defects significantly decrease the forward voltage for green LEDs.
PHYSICAL REVIEW APPLIED
(2022)
Article
Physics, Applied
Feng Wu, Jacob Ewing, Cheyenne Lynsky, Michael Iza, Shuji Nakamura, Steven P. DenBaars, James S. Speck
Summary: In this article, the authors used advanced characterization techniques to study the active region compositions, V-defect formation, and V-defect structure in green and red LEDs. They identified two types of V-defects, one that promotes hole injection and one that is believed to be deleterious to high-efficiency LEDs.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Nanoscience & Nanotechnology
Matthew S. Wong, Aditya Raj, Hsun-Ming Chang, Vincent Rienzi, Feng Wu, Jacob J. Ewing, Emily S. Trageser, Stephen Gee, Nathan C. Palmquist, Philip Chan, Ji Hun Kang, James S. Speck, Umesh K. Mishra, Shuji Nakamura, Steven P. DenBaars
Summary: The electrical performance of III-nitride blue micro-light-emitting diodes (mu LEDs) with different tunnel junction (TJ) architectures grown by metalorganic chemical vapor deposition is investigated. The introduction of AlGaN layer above the n-side of the TJ layer improves the current density-voltage characteristic and the effects of AlGaN/GaN superlattices are examined. The band diagram simulation shows that a net positive polarization charge is formed at the AlGaN/GaN interface, leading to a reduction in tunneling distance and an increase in tunneling probability. Additionally, the proposed AlGaN-enhanced TJ design significantly enhances the wall-plug efficiency of mu LEDs.
Article
Multidisciplinary Sciences
Jun-Yu Huang, Hsiao-Chun Hung, Kung-Chi Hsu, Chia-Hsun Chen, Pei-Hsi Lee, Hung-Yi Lin, Bo-Yen Lin, Man-kit Leung, Tien-Lung Chiu, Jiun-Haw Lee, Richard H. H. Friend, Yuh-Renn Wu
Summary: In this study, a model of steady state and time-dependent exciton diffusion, including singlet and triplet excitons, is developed. It is coupled with a modified Poisson and drift-diffusion solver to explain the mechanism of hyper triplet-triplet fusion (TTF) organic light-emitting diodes (OLEDs). Various characteristics of OLEDs are demonstrated using this modified simulator, and it can also be used to explain the mechanism of hyper-TTF-OLEDs and analyze the loss from different exciton mechanisms. Furthermore, optimizations of hyper-TTF-OLEDs are performed, increasing the internal quantum efficiency by approximately 33%.
ADVANCED THEORY AND SIMULATIONS
(2023)
Article
Physics, Applied
Kuan-Hao Chiao, Yuh-Renn Wu
Summary: This paper investigates the switching behaviors of SOT-MRAM utilizing a heavy metal/ferromagnet bilayer with an additional heavy metal capping strip, and reveals the mechanism and the importance of device parameters for deterministic switching and lower power consumption. The study provides fundamental insights into deterministic switching for SOT-MRAM with an additional heavy metal capping strip, which is valuable for practical applications.
APPLIED PHYSICS LETTERS
(2023)
Article
Chemistry, Analytical
Yao-Luen Shen, Chih-Yao Chang, Po-Liang Chen, Cheng-Chan Tai, Tian-Li Wu, Yuh-Renn Wu, Chih-Fang Huang
Summary: In this study, AlGaN/GaN light-emitting HEMTs with different locations of a single quantum well are fabricated and analyzed. The experiment demonstrates that confining the radiative recombination in the quantum well significantly shifts the light-emitting wavelength. Epi B, with a quantum well above the AlGaN barrier layer, shows superior intensity and uniformity in light-emitting compared to Epi A, which has a quantum well underneath the barrier.
Article
Crystallography
Vineeta R. Muthuraj, Wenjian Liu, Henry Collins, Weiyi Li, Robert Hamwey, Steven P. DenBaars, Umesh K. Mishra, Stacia Keller
Summary: The electrical properties of InN make it a promising candidate for III-nitride electronic devices. One-dimensional InN quantum wire-like structures were grown on miscut substrates using N-polar MOCVD growth to mitigate the high lattice mismatch with GaN. The optimal growth conditions for quantum wire segment formation were determined by varying the InN growth temperature, thickness, and NH3 flow during growth. Anisotropic electrical conduction was observed in the N-polar InN wire-like samples.
Article
Chemistry, Multidisciplinary
Hwan-Hee Cho, Sebastian Gorgon, Hsiao-Chun Hung, Jun-Yu Huang, Yuh-Renn Wu, Feng Li, Neil C. Greenham, Emrys W. Evans, Richard H. Friend
Summary: This research reports highly efficient and bright doublet electroluminescence devices by combining a thermally activated delayed fluorescence (TADF) host and a tris(2,4,6-trichlorophenyl)methyl-based radical emitter. The study shows improved efficiency roll-off at high current densities, making this technology more promising for practical applications.
ADVANCED MATERIALS
(2023)
Article
Optics
Chien-Chung Lin, Yuh-Renn Wu, Hao-Chung Kuo, Matthew S. Wong, Steven P. Denbaars, Shuji Nakamura, Ayush Pandey, Zetian Mi, Pengfei Tian, Kazuhiro Ohkawa, Daisuke Iida, Tao Wang, Yuefei Cai, Jie Bai, Zhiyong Yang, Yizhou Qian, Shin-Tson Wu, Jung Han, Chen Chen, Zhaojun Liu, Byung-Ryool Hyun, Jae-Hyun Kim, Bongkyun Jang, Hyeon-Don Kim, Hak-Joo Lee, Ying-Tsang Liu, Yu-Hung Lai, Yun-Li Li, Wanqing Meng, Haoliang Shen, Bin Liu, Xinran Wang, Kai-ling Liang, Cheng-Jhih Luo, Yen-Hsiang Fang
Summary: Micro light-emitting diode (micro-LED) is expected to play a significant role in future smart displays, offering advantages in various applications. The article focuses on the current status, challenges, and potential advances in micro-LED technology, highlighting the importance of epitaxy innovation and quantum scale structures. Peripheral components and technologies, such as microchip transfer and repair, heterogeneous integration, and novel 2D materials, are also discussed. The potential of micro-LED displays in augmented reality (AR) and the efforts to address existing problems are emphasized.
JOURNAL OF PHYSICS-PHOTONICS
(2023)
Article
Materials Science, Multidisciplinary
Wan Ying Ho, Abdullah I. Alhassan, Cheyenne Lynsky, Yi Chao Chow, Daniel J. Myers, Steven P. DenBaars, Shuji Nakamura, Jacques Peretti, Claude Weisbuch, James S. Speck
Summary: Using electron emission spectroscopy, researchers measured and analyzed the energy distribution of vacuum emitted electrons from electrically driven InGaN/GaN green light emitting diodes (LEDs) with and without a prewell superlattice (SL). They discovered a high-energy upper valley peak at approximately 1.7 eV above the I' valley in samples without a prewell SL, which is attributed to trap-assisted Auger recombination (TAAR). The absence of this peak in the sample with a prewell SL suggests the gettering of unidentified impurities that act as TAAR centers.
