Article
Engineering, Electrical & Electronic
Adreen Azman, Anas Kamarundzaman, Ahmad Shuhaimi Abu Bakar, Wan Haliza Abd Majid
Summary: The study investigated the properties of non-polar m-plane GaN layers grown on m-plane sapphire substrate using metal organic chemical vapor deposition at different disilane and Cp2Mg flow rates. The results show that higher flow rates lead to increased electron and hole concentrations due to doping, with an increase in electron mobility but a decrease in hole mobility. Implementing optimized n- and p-type contact layers resulted in a 483 nm non-polar LED with specific characteristics.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2021)
Article
Nanoscience & Nanotechnology
Hoe-Min Kwak, Jongil Kim, Je-Sung Lee, Jeongwoon Kim, Jaeyoung Baik, Soo-Young Choi, Sunwoo Shin, Jin-Soo Kim, Seung-Hyun Mun, Kyung-Pil Kim, Sang Ho Oh, Dong-Seon Lee
Summary: This study presents an approach for growing and exfoliating GaN on 2D material/GaN templates. The key is to protect the integrity of the 2D material in high-temperature growth conditions. With effective protection, GaN can endure high temperatures and still be exfoliated.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Materials Science, Ceramics
Kai Chen, Yachao Zhang, Jincheng Zhang, Xing Wang, Yixin Yao, Jinbang Ma, Yue Hao
Summary: By analyzing the growth modes of GaN films on AlN buffer layers with different thicknesses, a new growth model of GaN on AlN buffer was proposed in this study. Under optimal conditions, AlGaN/GaN/AlN heterostructures showed excellent performance.
CERAMICS INTERNATIONAL
(2022)
Article
Physics, Applied
Zhenghao Chen, Xuelin Yang, Danshuo Liu, Zidong Cai, Huayang Huang, Liwen Sang, Fujun Xu, Xinqiang Wang, Weikun Ge, Bo Shen
Summary: Controlling the partial pressure of NH3 is crucial for reducing the carbon impurity in GaN drift layers, leading to high mobility GaN vertical power devices. The study shows that the NH3 partial pressure is the key parameter in determining the carbon concentration. By increasing the NH3 partial pressure, the surface N vacancy concentration decreases, resulting in lower carbon incorporation efficiency. This approach effectively lowers the carbon concentration to 1.7 x 10(15)/cm(3) and achieves a record high electron mobility of 1227 cm(2)/Vs at room temperature, paving the way for high performance kV-class GaN vertical power devices on Si substrates.
APPLIED PHYSICS LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Peng Wu, Jianping Liu, Lingrong Jiang, Lei Hu, Xiaoyu Ren, Aiqin Tian, Wei Zhou, Masao Ikeda, Hui Yang
Summary: The growth behaviors of GaN on patterned GaN substrate were investigated in this study. Spiral and nucleation growth were observed after the elimination of miscut-induced atomic steps. The morphology of nucleation growth at different temperatures was explained by introducing a multi-nucleation regime with critical supersaturation. Simulated results based on a step motion model successfully elucidated the growth behaviors on stripes. These findings have practical implications for controlling the surface kinetics of devices, such as laser diodes, grown on patterned substrates.
Article
Chemistry, Multidisciplinary
Dahee Seo, Sunjae Kim, Hyeong-Yun Kim, Dae-Woo Jeon, Ji-Hyeon Park, Wan Sik Hwang
Summary: The formation of n-Ga2O3/p-GaN heterojunctions has been intensively studied due to the lack of p-Ga2O3. In this work, single-crystalline β-Ga2O3 is grown on a GaN (001)/Al2O3 substrate using MOCVD, and an abrupt heterojunction without a noticeable interfacial layer is observed between β-Ga2O3 and GaN. However, due to the lattice mismatch, grain boundaries and defects are present in β-Ga2O3 originating from the Ga2O3/GaN interface. This work marks an important step towards the formation of high-quality Ga2O3/GaN heterojunctions for various devices.
CRYSTAL GROWTH & DESIGN
(2023)
Article
Materials Science, Coatings & Films
Yifeng Xu, Xiong Zhang, Ruiting Fang, Xuguang Luo, Lin Chen, Shenyu Xu, Zhiyi Lou, Jia Cui, Guohua Hu
Summary: Nonpolar a-plane GaN films with 3D GaN layers were successfully grown on r-plane sapphire substrates by metal organic chemical vapor deposition. The characteristics of the grown films were further improved by treating the inserted 3D GaN layers with Si, Mg, and In. The introduction of Si-treated 3D GaN layer resulted in significant improvements in crystalline quality, anisotropy reduction, and optical property of the nonpolar a-plane GaN film.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Materials Science, Multidisciplinary
Yuntao Zhao, Guanghui Li, Shuai Zhang, Linkai Yi, Haoran Qi, Feng Liang, Jing Yang, Mei Zhou, Huixing Shen, Degang Zhao
Summary: Four InGaN/GaN multi-quantum well samples with different growth rates were studied, showing that the growth rate has a significant impact on the uniformity and internal quantum efficiency of the samples. The best uniformity was observed at a growth rate of 0.0125 nm s(-1), while the highest IQE at room temperature was achieved at a growth rate of 0.034 nm s(-1).
MATERIALS RESEARCH EXPRESS
(2021)
Article
Chemistry, Physical
Xueru Cai, Yiming Ma, Jinlong Ma, Dongwei Xu, Xiaobing Luo
Summary: The study reveals that the structural and electronic band gap properties of m-plane GaN vary with the number of atomic layers, leading to unique layer-dependent changes and transitions in band gap type. By examining the relationship between structure and electronic band gap, it is shown that the unsaturated surface structure plays a crucial role in the band gap type transition.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2021)
Article
Chemistry, Physical
Haoran Sun, Yuhui Chen, Yuhao Ben, Hongping Zhang, Yujie Zhao, Zhihao Jin, Guoqi Li, Mei Zhou
Summary: In this study, GaN cap layers with different thicknesses were grown on each InGaN well layer during MOCVD growth of InGaN/GaN multiple quantum well (MQW) samples to investigate the impact of the cap layer on the photoluminescence (PL) characteristics of MQWs. Temperature-dependent PL spectra revealed that when the cap layer was too thick, the localized states of the quantum wells became relatively non-uniform, with worse uniformity observed in thicker well layers. Micro-area fluorescence imaging tests further confirmed that thicker cap layers resulted in poorer luminescence quality of the quantum wells. In summary, a relatively thin cap layer during growth can improve the uniformity of localized states and the luminescence characteristics of quantum wells, which is beneficial for the preparation of highly efficient QWs, particularly for green LEDs.
Article
Materials Science, Multidisciplinary
Akanksha Kapoor, Vincent Grenier, Eric Robin, Catherine Bougerol, Gwenole Jacopin, Bruno Gayral, Maria Tchernycheva, Joel Eymery, Christophe Durand
Summary: A dual-color emission is achieved by combining two monolithic sets of core-shell multiple quantum wells (MQWs) grown on GaN microwires, showing blue and green emissions. Advanced structural characterization reveals the growth of two sets of MQWs and their color emission sources on m-plane sidewall surfaces. LED based on these core-shell MQWs can be fabricated with multiple color emission possibilities.
ADVANCED PHOTONICS RESEARCH
(2021)
Article
Physics, Applied
Yingying Lin, Hadi Sena, Martin Frentrup, Markus Pristovsek, Yoshio Honda, Hiroshi Amano
Summary: The stress relaxation of Al0.19Ga0.81N grown by metal-organic vapor phase epitaxy on quasi-bulk GaN substrates was studied using x-ray diffraction. The anisotropic in-plane stress caused orthorhombic distortion of the lattice. A mathematical method was developed to calculate the distortion along different directions and obtained the lattice parameters, Al content, and strain values. The stress relaxation in the two in-plane directions involved different mechanisms, with misfit dislocations and crack formation being the dominant methods of relaxation.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Eisuke Kanao, Katsuya Nakano, Ryoma Kamei, Takuro Hosomi, Yasushi Ishihama, Jun Adachi, Takuya Kubo, Koji Otsuka, Takeshi Yanagida
Summary: In this study, the hidden molecular recognition abilities of ZnO nanowires were explored via liquid chromatography. The results showed that ZnO nanowires exhibited a stronger intermolecular interaction with phenylphosphoric acid and specifically recognized the phosphate groups in nucleotides, with the interaction increasing with the number of phosphate groups. This unique molecular selectivity was attributed to the surface properties of ZnO nanowires.
NANOSCALE ADVANCES
(2022)
Article
Physics, Applied
Purun-hanul Kim, Sang Ho Jeon, Jin Hyuk Jang, Seungwu Han, Youngho Kang
Summary: Micro-light-emitting diodes (mu LEDs) based on GaN are important for future displays, but surface e -h recombination can decrease device efficiency. This study investigates the impact of Ga (VGa) and N (VN) vacancies on the GaN m plane, which are created during the production of one-dimensional GaN structures. The results show that surface VGa doesn't significantly contribute to nonradiative recombination, while surface VN has a deep defect state near the midgap and may act as useful recombination centers due to its low formation energy and small energy barriers for electron and hole capture.
PHYSICAL REVIEW APPLIED
(2023)
Article
Materials Science, Multidisciplinary
Krishna Yaddanapudi, Sabyasachi Saha, Kuttanellore Muraleedharan, Dipankar Banerjee
Summary: This study demonstrates the influence of metalorganic chemical vapor deposition process parameters on the evolution of gallium nitride (GaN) and focuses on nitrogen-polar GaN (N-polar GaN). The research shows that N-polar GaN epilayers formed at low epilayer growth temperatures have high surface quality and good crystalline quality.
MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
S. M. Sadaf, Y. H. Ra, T. Szkopek, Z. Mi
Article
Chemistry, Multidisciplinary
Yong-Ho Ra, Renjie Wang, Steffi Y. Woo, Mehrdad Djavid, Sharif Md. Sadaf, Jaesoong Lee, Gianluigi A. Botton, Zetian Mi
Article
Chemistry, Multidisciplinary
S. M. Sadaf, S. Zhao, Y. Wu, Y. -H. Ra, X. Liu, S. Vanka, Z. Mi
Article
Materials Science, Multidisciplinary
Rishabh Raj, Veeramuthu Vignesh, Yong-Ho Ra, Rajkumar Nirmala, Cheul-Ro Lee, Rangaswamy Navamathavan
JOURNAL OF PHOTONICS FOR ENERGY
(2017)
Article
Materials Science, Multidisciplinary
Yong-Ho Ra, San Kang, Cheul-Ro Lee
ADVANCED OPTICAL MATERIALS
(2018)
Article
Nanoscience & Nanotechnology
Yong-Ho Ra, Cheul-Ro Lee
Article
Chemistry, Multidisciplinary
Yong-Ho Ra, Cheul-Ro Lee
Article
Multidisciplinary Sciences
Yong-Ho Ra, Roksana Tonny Rashid, Xianhe Liu, Sharif Md. Sadaf, Kishwar Mashooq, Zetian Mi
Article
Chemistry, Multidisciplinary
Sung-Un Kim, Yong-Ho Ra
Summary: The study successfully developed high-concentration InGaN and long-InGaN nanowire heterostructures on silicon substrate using molecular beam epitaxy (MBE) system, improving crystal quality and significantly enhancing optical properties.
Article
Engineering, Electrical & Electronic
Sung-Un Kim, Jeong-Kyun Oh, Dae-Young Um, Bagavath Chandran, Cheul-Ro Lee, Yong-Ho Ra
Summary: In this study, sub-micron monolithic full-color R/G/B nanorod LEDs with an Al core-shell reflector were designed, which significantly improved the light extraction efficiency. The unique design of the submicron pixel will be a key factor in enabling the next generation of AR and VR displays that require ultra-small and compact pixels.
IEEE PHOTONICS JOURNAL
(2023)
Article
Nanoscience & Nanotechnology
Sung-Un Kim, Dae-Young Um, Jeong-Kyun Oh, Bagavath Chandran, Cheul-Ro Lee, Yong-Ho Ra
Summary: In this study, selective area epitaxial growth of a novel GaN nanorod-based LD tunnel-junction structure incorporating a photonic crystal effect was demonstrated. The nanorod-based DBR-free GaN LD structure with the photonic crystal effect was shown to be a surface-emitting laser diode that emits light in a vertical direction. The fabricated GaN nanorod laser diode device exhibited lasing performance at a wavelength of 502 nm with a full width at half-maximum of 0.98 nm. Additionally, a low turn-on voltage was achieved by the novel tunnel junction-based n-GaN to metal contact structure, leading to significant improvement in light efficiency even during long operating times. This unique 5 μm x 5 μm nanorod LD device not only proves useful for future display pixels requiring high brightness and ultra-high definition, but also opens up new possibilities for nano-optoelectronic devices in the future.
Article
Crystallography
Soyeon An, Dae-Woo Jeon, Jonghee Hwang, Yong-Ho Ra
JOURNAL OF THE KOREAN CRYSTAL GROWTH AND CRYSTAL TECHNOLOGY
(2019)
Article
Chemistry, Multidisciplinary
Yong-Ho Ra, Roksana Tonny Rashid, Xianhe Liu, Jaesoong Lee, Zetian Mi
ADVANCED FUNCTIONAL MATERIALS
(2017)
Proceedings Paper
Engineering, Electrical & Electronic
Renjie Wang, Yong-Ho Ra, Yuanpeng Wu, Songrui Zhao, Hieu. P. T. Nguyen, Ishiang Shih, Zetian Mi
GALLIUM NITRIDE MATERIALS AND DEVICES XI
(2016)
Proceedings Paper
Engineering, Electrical & Electronic
Rishabh Raj, Yong-Ho Ra, Cheul-Ro Lee, Sonika Obheroi, R. Navamathavan
GALLIUM NITRIDE MATERIALS AND DEVICES XI
(2016)
Article
Chemistry, Multidisciplinary
Abu Talha Aqueel Ahmed, Sankar Sekar, Shubhangi S. Khadtare, Nurul Taufiqu Rochman, Bathula Chinna, Abu Saad Ansari
Summary: In this study, MnCo2S4 nanosheet catalyst was successfully synthesized and found to exhibit superior performance in hydrogen evolution. Compared to MnCo2S4, MnCo2S4 showed low overpotentials, moderate Tafel slope, and excellent sustainability. The outstanding performance can be attributed to the increased number of electrochemically active sites and enhanced electronic conductivity on the catalyst surface.
Article
Chemistry, Multidisciplinary
Victor V. Maltsev, Elena A. Volkova, Elizaveta V. Koporulina, Diana D. Mitina, Vladimir L. Kosorukov, Anna I. Jiliaeva, Daniil A. Naprasnikov, Konstantin N. Gorbachenya, Viktor E. Kisel
Summary: The phase relationships, crystal properties and luminescence kinetics of two complex systems were studied, including unit cell parameters, segregation coefficients of impurities, and lifetimes of energy levels.
Article
Chemistry, Multidisciplinary
Xiaoman Zhang, Wangwang Xu, W. J. Meng, Andrew C. Meng
Summary: This study successfully grew high-quality single crystal AlScN nanowires through ultra-high vacuum reactive sputtering technique and characterized their structure and properties. The nanowires exhibit significantly reduced mosaic spread and predominantly single ferroelectric domains, as well as a high piezoelectric constant.
Article
Chemistry, Multidisciplinary
Tom E. de Vries, Elias Vlieg, Rene de Gelder
Summary: Networks are important for describing relationships between people, roads between cities, reactions between chemicals, and other interactions. Bipartiteness, dividing the network into two groups, can facilitate the study of the network's structure. We have developed an algorithm that can find a near-optimal bipartisation within a reasonable time frame and used it to uncover the hidden structure of the CSD cocrystal network.
Article
Chemistry, Multidisciplinary
Chuchu Han, Jing Yang, Xin Zhang, Aisen Li, Jiang Peng
Summary: An elastic crystal based on a photo-reactive acylhydrazone derivative is reported, which exhibits reversible bending behavior under UV irradiation and heating. The crystal undergoes reversible E<->Z isomerization under light and heating conditions. The crystal demonstrates excellent elastic properties and the bending can be controlled to control the output direction of red light.
Article
Chemistry, Multidisciplinary
Lingfeng Zhang, Yu Wang, Yefeng Wang, Shuai Liu, Na Zhang, Mingmin Yang, Haixia Ma, Zhaoqi Guo
Summary: This study designs and synthesizes a series of high-energy salts compounds without heavy metal ions and azide groups. The molecular structures and stability of the compounds are confirmed through single-crystal X-ray diffraction and intermolecular interaction analysis. Furthermore, the thermal stability, energetic properties, and electrical initiation properties of the compounds are investigated, suggesting their potential as primary explosives.
