Article
Nanoscience & Nanotechnology
Thomas Kanne, Mikelis Marnauza, Dags Olsteins, Damon J. Carrad, Joachim E. Sestoft, Joeri de Bruijckere, Lunjie Zeng, Erik Johnson, Eva Olsson, Kasper Grove-Rasmussen, Jesper Nygard
Summary: Semiconductor-superconductor hybrids play a crucial role in realizing complex quantum phenomena. By utilizing InAs nanowires and epitaxially matched Pb films, a new parameter space has been opened up, allowing for the exploration of exotic quantum regimes. The development of such hybrids with superior characteristics offers new possibilities for applications in topological superconductivity and quantum computation.
NATURE NANOTECHNOLOGY
(2021)
Article
Materials Science, Multidisciplinary
Philipp Storm, Susanne Selle, Holger von Wenckstern, Marius Grundmann, Michael Lorenz
Summary: Transparent, p-type semiconductor copper iodide (CuI) thin films were grown via pulsed laser deposition on SrF2(111) using water soluble sacrificial layers of sodium bromide (NaBr). The resulting CuI thin films are single crystalline with reduced surface roughness compared to epitaxial CuI grown with rotational domains on other templates. The CuI thin films were subsequently transferred onto glass using epoxy/glue and dissolution of NaBr in a water-vapor atmosphere.
JOURNAL OF MATERIALS CHEMISTRY C
(2022)
Article
Materials Science, Multidisciplinary
M. Tyunina, L. L. Rusevich, E. A. Kotomin, O. Pacherova, T. Kocourek, A. Dejneka
Summary: The introduction of oxygen vacancies in thin films of perovskite oxide SrTiO3 can stabilize epitaxy and increase lattice strain, facilitating the growth of strained films. This phenomenon is expected to be relevant for a broad range of functional oxides due to the inherent anisotropic nature of oxygen-vacancy stresses in perovskite-type and many other oxides.
JOURNAL OF MATERIALS CHEMISTRY C
(2021)
Article
Chemistry, Physical
Saeed Moayedpour, Derek Dardzinski, Shuyang Yang, Andrea Hwang, Noa Marom
Summary: A new version of the Ogre open source Python package has been introduced, enabling structure prediction of epitaxial inorganic interfaces through lattice and surface matching. The package includes a lattice matching step and a surface matching step, with geometric and similarity score functions used for optimization and ranking of interfaces. Applications of Ogre for Al/InAs and Fe/InSb interfaces demonstrate automated DFT calculations of interface properties.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Nanoscience & Nanotechnology
Xiao Tang, Kuang-Hui Li, Yue Zhao, Yanxin Sui, Huili Liang, Zeng Liu, Che-Hao Liao, Wedyan Babatain, Rongyu Lin, Chuanju Wang, Yi Lu, Feras S. Alqatari, Zengxia Mei, Weihua Tang, Xiaohang Li
Summary: The study demonstrates the epitaxial growth of technically important beta-Ga2O3 semiconductor thin films on flexible CeO2(001)-buffered Hastelloy tape, leading to the fabrication of flexible photodetectors with excellent photoelectrical performance. The photodetectors exhibit a responsivity of 4 X 10(4) mA/W and remain robust after more than 20,000 bending test cycles, showing potential for future applications in flexible oxide semiconductor devices.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Materials Science, Multidisciplinary
Fang Li, Yani An, Tiefeng Yang, Changlin Yu
Summary: In this study, a bilayer MoS2/MoSe2 vdW heterostructure with an atomic-layer clean interface was successfully prepared using an iodine-assisted growth strategy, and it was shown to exhibit enhanced photoresponsivity. This study provides an important reference for the controlled growth of TMDs vdW heterostructures.
Article
Chemistry, Multidisciplinary
Nguyen Ngan Nguyen, Hyo Chan Lee, Kangkyun Baek, Min Seok Yoo, Hansol Lee, Hyungsub Lim, Shinyoung Choi, Cheol-Joo Kim, SungWoo Nam, Kilwon Cho
Summary: The hybrid graphene template enables the preparation of highly crystalline organic semiconductor thin films with large grain sizes. Compared to conventional graphene templates, phototransistors fabricated on this hybrid template exhibit significantly higher photoresponsivity.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Zachary R. Lindsey, Malachi West, Peter Jacobson, John Robert Ray
Summary: Compared to Si, GaAs has advantages such as high carrier mobility and energy conversion efficiency, making it a leading competitor in optoelectronics and solar energy conversion. This research demonstrates the electrodeposition and controlled alloying of polycrystalline InxGa1-xAs films at ambient pressure and near-room temperature using the electrochemical liquid-liquid-solid (ec-LLS) process.
CRYSTAL GROWTH & DESIGN
(2022)
Article
Physics, Condensed Matter
M. A. A. Z. Md Sahar, Z. Hassan, S. S. Ng, N. A. Hamzah, Y. Yusuf, N. N. Novikova, V. A. Yakovlev, S. A. Klimin
Summary: This study demonstrates the growth transition of AlN films from 3D to 2D on a sapphire substrate at different temperatures using MOCVD. The results show that as the temperature increases, the AlN film exhibits a smoother surface and higher crystal quality. The film grown at 1100℃ in the Frank-van der Merwe or 2D growth mode has the highest crystalline quality.
SUPERLATTICES AND MICROSTRUCTURES
(2022)
Article
Materials Science, Multidisciplinary
Sanjoy Kumar Mazumder, Kaustubh Bawane, J. Matthew Mann, Aaron French, Lin Shao, Lingfeng He, Anter El-Azab
Summary: The effect of isochronal annealing on the evolution of dislocation loop and void population in proton irradiated ThO2 has been investigated. Isochronal annealing at different temperatures showed insignificant growth and coarsening of self-interstitial atom (SIA) dislocation loops. Nanometric voids were observed at high annealing temperatures. Cluster dynamics (CD) model predicted the nucleation, growth, and coarsening of defects but did not account for their migration and coalescence due to elastic interaction. The CD model also predicted the evolution of nanometric voids.
JOURNAL OF NUCLEAR MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Maudud Ahmed, Shubharaj Mukherjee, Tukai Singha, P. M. G. Nambissan
Summary: In this study, cadmium oxide nanocrystallites with sizes ranging from 16 nm to 30 nm were synthesized via a chemical precipitation method at different synthesis temperatures. X-ray diffraction analysis confirmed the absence of mixed or impurity phases. The samples exhibited quantum confinement effects, as demonstrated by the variation in band gap energies measured by optical absorption. The presence of defects, such as non-stoichiometric defects, was found to greatly influence the properties of the nanocrystallites, and their concentration was quantified using positron annihilation studies.
JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS
(2023)
Article
Chemistry, Physical
Lan Zhou, Maoliang Xie, Hang Su, RunLin Chen, Yuxia Pang, Hongming Lou, Dongjie Yang, Xueqing Qiu
Summary: Papermaking wastewater with high output and COD seriously impacts the water environment. Lignin, a by-product of the papermaking industry, is the main contaminant responsible for excessive COD. Bismuth oxide has been identified as a potential catalyst for the photocatalytic degradation of lignin-contained wastewater due to its high charge conduction performance and light corrosion resistance. However, the low degradation efficiency of pure Bi2O3 is attributed to its high electron-hole recombination rate and poor surface chemical state. To overcome this, an OV-Bi2O3/BiOCOOH heterojunction with oxygen vacancies and heterojunction coexisting was designed. The degradation efficiency of OV-Bi2O3/BiOCOOH is significantly higher compared to pure Bi2O3 and BiOCOOH, approximately 3 and 16 times, respectively. This improvement in photocatalytic performance can be attributed to the synergy between the heterojunction and oxygen vacancy, while the covalent bonds ensure stability.
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
(2023)
Article
Physics, Applied
Yoshisuke Ban, Kimihiko Kato, Shota Iizuka, Shigenori Murakami, Koji Ishibashi, Satoshi Moriyama, Takahiro Mori, Keiji Ono
Summary: In order to achieve high-temperature operation of Si qubits, deep impurity levels with large confinement energy were introduced into Si wafers to minimize thermal excitation. Group II impurity Zn and group VI impurities S and Se were introduced into Si substrates using ion implantation, known for forming deep levels. The concentration-depth profiles, energy level depths, and absence of defects of these samples were analyzed. Conditions for introducing deep impurities into 50 nm thick Si channels were identified, and the formation of deep levels and absence of defects were experimentally confirmed. Using the obtained conditions, single-electron transport at room temperature, high-temperature operation of qubits, and room-temperature quantum magnetic sensors are promising.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Engineering, Electrical & Electronic
Borislav Hinkov, Hanh T. Hoang, Maxime Hugues, Jean-Michel Chaveau, Gottfried Strasser
Summary: Zinc oxide is a novel material system for mid-infrared and THz optoelectronics, with the non-polar m-plane orientation showing promise for device design. A new ICP-RIE process has been developed for etching m-Zn(Mg)O heterostructures, achieving smooth vertical sidewalls and high selectivity towards a SiN etch mask. Surface leakage currents in etched m-plane Zn(Mg)O structures can be significantly suppressed by treatment in hydrogen peroxide (H2O2).
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2021)
Article
Engineering, Electrical & Electronic
Jingyang Zhang, Wei Huang, Zhihao Su, Zhiwen Liang, Qi Wang, Au Yeng Wai Lun, D. W. Zhang, Zhaojun Liu
Summary: This letter introduces a new method for controlling UV light emitters by directly modifying the HEMT drain, using the recombination of p-GaN and 2DEG to achieve luminescence. The method demonstrates a novel approach of converting electronic devices into light-emitting devices, different from traditional integration.
IEEE ELECTRON DEVICE LETTERS
(2022)
Article
Physics, Condensed Matter
Mylene Sauty, Natalia Alyabyeva, Cheyenne Lynsky, Yi Chao Chow, Shuji Nakamura, James S. Speck, Yves Lassailly, Alistair C. H. Rowe, Claude Weisbuch, Jacques Peretti
Summary: In this study, scanning tunneling electroluminescence microscopy was used to investigate the unique radiative recombination properties near a defect in an InGaN/GaN quantum well. The results revealed intense emission peaks at higher energies close to the defect edges, which were not visible in the macrophotoluminescence spectrum. The quantitative information obtained from fitting the local tunneling electroluminescence spectra provided important insights into carrier localization in the quantum well.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
(2023)
Article
Engineering, Electrical & Electronic
R. M. Cadena, D. R. Ball, E. X. Zhang, S. Islam, A. Senarath, M. W. McCurdy, E. Farzana, J. S. Speck, N. Karom, A. O'Hara, B. R. Tuttle, S. T. Pantelides, A. F. Witulski, K. F. Galloway, M. L. Alles, R. A. Reed, D. M. Fleetwood, R. D. Schrimpf
Summary: Low-energy ion-induced breakdown and single event burnout (SEB) were observed in beta-gallium oxide (beta-Ga2O3) Schottky diodes at voltages lower than expected. Different responses were observed for alpha particles, Cf-252, and heavy-ion irradiation. TCAD simulations explained the breakdown as a result of ion strikes and defect-driven breakdown due to displacement-damage-induced defects in beta-Ga2O3. First-principles calculations showed the formation of less resistive defect clusters that can lead to destruction at reduced voltages.
IEEE TRANSACTIONS ON NUCLEAR SCIENCE
(2023)
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
Optics
Panpan Li, Hongjian Li, Yifan Yao, Kai Shek Qwah, Mike Iza, James S. Speck, Shuji Nakamura, Steven P. Denbaars
Summary: In this work, we demonstrate the vertical integration of nitride-based blue/green micro-light-emitting diode (mu LED) stacks with independent junction control using a hybrid tunnel junction (TJ). The hybrid TJ was grown by metal-organic chemical vapor deposition (p + GaN) and molecular-beam epitaxy (n + GaN). Different junction diodes were able to generate uniform blue, green, and blue/green emissions. The peak external quantum efficiency (EQE) of the TJ blue mu LEDs and green mu LEDs with indium tin oxide contact were 30% and 12%, respectively. Carrier transportation between different junction diodes was discussed. This work suggests a promising approach for vertical mu LED integration to enhance the output power of single LED chips and monolithic mu LEDs with different emission colors and independent junction control.
Article
Engineering, Electrical & Electronic
M. Ikram Md Taib, M. A. Ahmad, E. A. Alias, A. Alhassan, I. A. Ajia, M. M. Muhammed, I. S. Roqan, S. P. DenBaars, J. S. Speck, S. Nakamura, N. Zainal
Summary: In-surfactant was introduced during the growth of high temperature GaN quantum barriers and GaN interlayer in InGaN/GaN green LEDs. Results showed that the introduction of In-surfactant improved LED growth, particularly in the GaN interlayer. It improved the morphology of the interlayer, allowed it to serve as a good surface growth, and effectively improved the multi-quantum wells. Moreover, the introduction of In-surfactant shifted the emission wavelength towards red, reduced the forward voltage of the LEDs, and allowed faster carrier decay lifetime.
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(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
Physics, Applied
Panpan Li, Hongjian Li, Yunxuan Yang, Matthew S. Wong, Mike Iza, Michael J. Gordon, James S. Speck, Shuji Nakamura, Steven P. DenBaars
Summary: This article presents high-performance 10 x 10 μm InGaN amber micro-size LEDs. At 15 A cm(-2), the InGaN micro LEDs exhibit a single emission peak at 601 nm. The peak external quantum efficiency (EQE) and wall-plug efficiency are 5.5% and 3.2%, respectively. Compared to the 100 x 100 μm InGaN red micro LEDs, the 10 x 10 μm InGaN red micro LEDs maintain a similar EQE value with the same efficiency droop. These results highlight the higher efficiency potential of InGaN materials compared to common AlInGaP materials for the ultra-small size red micro LEDs required by augmented reality and virtual reality displays.
APPLIED PHYSICS EXPRESS
(2023)
Article
Physics, Applied
Wan Ying Ho, Yi Chao Chow, Shuji Nakamura, Jacques Peretti, Claude Weisbuch, James S. Speck
Summary: Electron emission spectroscopy was performed on metalorganic chemical vapor deposition grown p-n(-)-n(+) junctions with p-thicknesses ranging from 50 to 300 nm, doped with [Mg] = 3.5 x 10(19) cm(-3). By measuring the decreasing emitted electron intensity from a cesiated p-GaN surface with increasing p-thickness, we were able to extract the minority carrier diffusion length of electron in p-type GaN, L-e = 2663 nm. The measured value is in good agreement with literature reported values. The extrapolated electron current at the n(-) region p-GaN interface is in reasonable agreement with the simulated electron current at the interface.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Fikadu Alema, Takeki Itoh, William Brand, Andrei Osinsky, James S. Speck
Summary: We investigated the controllable nitrogen doping of beta-Ga2O3 using ammonia diluted in nitrogen as a source of active nitrogen. The study looked at the effects of flow rate and substrate temperature on the doping efficiency and reproducibility. By increasing the flow rate of NH3/N-2, the nitrogen impurities incorporated into beta-Ga2O3 increased linearly. The presence of hydrogen in the film accompanied the nitrogen doping at low substrate temperatures.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Y. C. Chow, C. Lynsky, S. Nakamura, S. P. DenBaars, C. Weisbuch, J. S. Speck
Summary: Efficiency droop at high current densities is a common problem for InGaN-based LEDs, especially for conventional c-plane devices. This study introduces a method to reduce the internal electric fields in c-plane quantum wells by using doped barriers, which allows for a thick active region design and leads to improved LED performance.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Optics
J. Mickevic, E. Valkiunaite, Z. Podlipskas, K. Nomeika, S. Nargelas, G. Tamulaitis, Y. C. Chow, S. Nakamura, J. S. Speck, C. Weisbuch, R. Aleksieju
Summary: The dynamics of two distinct bands in non-polar m-plane InGaN/GaN multiple quantum wells (MQWs) were investigated using PL, CL, and DT spectroscopy. The shift in peak emission wavelength with increasing excitation was caused by competition between these bands. DT measurements attributed the high-energy PL band to optical transitions between ground QW states, while the low-energy PL band was associated with recombination of localized carriers. CL measurements confirmed the dispersion of deep localized states and suggested small-scale disorder. PL measurements showed that localized states are highly sensitive to indium content and structural parameters. Temperature-dependent PL studies revealed strong carrier-phonon interaction.
JOURNAL OF LUMINESCENCE
(2023)
Article
Psychology, Developmental
Erin P. Vaughan, Julianne S. Speck, Paul J. Frick, Toni M. Walker, Emily L. Robertson, James V. Ray, Tina D. Wall Myers, Laura C. Thornton, Laurence Steinberg, Elizabeth Cauffman
Summary: Research on proactive and reactive aggression in adolescents and young adults found that these two types of aggression have unique developmental trajectories and distinct covariates. Proactive aggression was influenced by callous-unemotional traits, while reactive aggression was predicted by impulsivity. These findings highlight the importance of considering the specific factors associated with each type of aggression in understanding and addressing aggressive behaviors.
DEVELOPMENT AND PSYCHOPATHOLOGY
(2023)
Article
Physics, Applied
Wan Ying Ho, Cameron W. Johnson, Tanay Tak, Mylene Sauty, Yi Chao Chow, Shuji Nakamura, Andreas Schmid, Jacques Peretti, Claude Weisbuch, James S. Speck
Summary: In this study, the lateral distribution of the junction current in an electrical biased p-n GaN diode was measured using electron emission microscopy with a low-energy electron microscope. The vacuum level on the diode surface was reduced by cesium deposition to achieve negative electron affinity, allowing emitted overflow electrons on the biased diode surface to be imaged for their spatial distribution. The obtained results were compared with Joyce and Wemple's analytical solutions [J. Appl. Phys. 41, 3818 (1970)] and showed a good match.
APPLIED PHYSICS LETTERS
(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.
Article
Physics, Applied
Saulius Marcinkevicius, Jacob Ewing, Rinat Yapparov, Feng Wu, Shuji Nakamura, James S. Speck
Summary: Hole injection through V-defect sidewalls into all quantum wells can increase the efficiency of long wavelength GaN light emitting diodes, allowing for population of all wells in a multiple QW structure.
APPLIED PHYSICS LETTERS
(2023)