Article
Nanoscience & Nanotechnology
Clemens Petersen, Sofie Vogt, Max Kneiss, Holger von Wenckstern, Marius Grundmann
Summary: Phase-pure alpha-Ga2O3 thin films were successfully grown on m-plane sapphire using pulsed laser deposition (PLD). The influence of growth temperature, oxygen background pressure, and film thickness on the structural properties was investigated. It was found that a growth window for phase-pure alpha-Ga2O3 could be achieved at temperatures above 480 degrees C and low oxygen pressures of 3 x 10(-4) mbar. The growth rate increased with increasing oxygen pressure and showed an Arrhenius-like decrease at lower temperatures. Thicker layers promoted the growth of monoclinic beta-Ga2O3. Mixed alpha-Ga2O3 and spinel-defective gamma-Ga2O3 were observed at higher oxygen pressures and lower temperatures.
Article
Physics, Applied
Sierra Seacat, John L. Lyons, Hartwin Peelaers
Summary: Ga2O3 is a promising wide-bandgap material, and the properties of its orthorhombic kappa phase can be tuned by alloying with In2O3 to increase lattice constants linearly and decrease bandgaps and conduction-band offsets nonlinearly.
APPLIED PHYSICS LETTERS
(2021)
Article
Chemistry, Physical
Jerzy Goraus, Jacek Czerniewski, Krystian Prusik, Marcin Fijalkowski
Summary: The study found that Ti2CrAl does not exhibit the expected magnetic ordering characteristic of HMF materials, with relatively moderate magnetoresistivity. Unexpected superconducting transition was observed in the sample below 6.5K, but without any Meissner effect or lambda-type hump.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Chemistry, Inorganic & Nuclear
Fatima Safieddine, Fouad El Haj Hassan, Michel Kazan
Summary: In this study, the FP-LAPW thorn lo method was used to investigate the properties of Ga2O3, including structural, electronic, elastic, optical, thermodynamic, and transport properties. The results show that Ga2O3 has potential applications in optoelectronics and thermoelectrics.
JOURNAL OF SOLID STATE CHEMISTRY
(2022)
Article
Materials Science, Ceramics
Esneyder Puello-Polo, Noemi R. Checca-Huaman, Elvis O. Lopez, Carlos A. T. Toloza, Franklin J. Mendez
Summary: The impact of the synthesis method on the properties of the Al2O3-Ga2O3 sample was investigated. Ga loading resulted in an increase in surface area and pore volume, but a decrease in pore size. XRD analysis confirmed the formation of γ-Al2O3 with Ga atoms incorporated into the structure. The adsorption affinity of the adsorbent was strongest for BT and weakest for DBT.
CERAMICS INTERNATIONAL
(2023)
Article
Physics, Condensed Matter
Prashant Singh, Debashish Das, Duane D. Johnson, Raymundo Arroyave, Aftab Alam
Summary: The study demonstrates that Pd alloying significantly influences the phase stability, electronic structure, and elastic properties of L1(0) Fe-Ni materials. Increasing Pd concentration alters the relative thermodynamic stability and elastic behavior of the material. Pd alloying also enhances the local Fe moment and structural anisotropy of the material.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2021)
Article
Chemistry, Physical
Hui Zeng, Meng Wu, Meijuan Cheng, Qiubao Lin
Summary: This study investigates the theoretical band structure calculations and optical properties of Cu- and Zn-doped α-Ga2O3. The results reveal the oxidation states and impurity band types and locations of Cu and Zn dopants in α-Ga2O3, which promote p-type conductivity. The optical calculations show that Cu and Zn dopants induce the migration of ultraviolet light to the visible-infrared region, which is associated with the impurity 3d orbitals near the Fermi level. This work may guide the design of p-type conductivity and innovative α-Ga2O3-based optoelectronic devices.
Article
Materials Science, Ceramics
Yixiao Qian, Bin Song, Junteng Jin, Genki I. Prayogo, Keishu Utimula, Kousuke Nakano, Ryo Maezono, Kenta Hongo, Gaoling Zhao
Summary: The effects of P2O5 content on the structural and mechanical properties of phosphoaluminosilicate glasses were studied using ab initio molecular dynamics simulations. It was found that an increase in the phosphorus content led to disordered distributions of bond length and bond angle, and significant contributions of P-O bonding strength to the elastic modulus were observed.
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
(2022)
Article
Energy & Fuels
Vipul Srivastava, Navdeep Kaur, Xiaotian Wang, Muhammad Mushtaq, Sajad Ahmad Dar
Summary: The Mn2PtCo Heusler alloy was studied for its structural, electronic, magnetic, mechanical, and thermodynamic properties using density functional theory. The alloy was found to have a ferromagnetic phase and metallic character with a magnetic moment in accordance with the Slater-Pauling rule. The analysis also revealed the brittle nature of the alloy. In addition, thermodynamic properties were estimated for potential applications in device fabrication.
INTERNATIONAL JOURNAL OF ENERGY RESEARCH
(2021)
Article
Materials Science, Ceramics
Guangran Zhang, Jiao Li, Yiquan Wu
Summary: Translucent ceramics consisting of monoclinic Ga2O3 and Ga2O3-Al2O3 solid solution were fabricated through a two-step sintering process. These ceramics exhibit high density and tunable band gap. Among them, Ga0.4Al1.6O3 ceramics show the highest total transmittance and prolonged photoluminescence.
CERAMICS INTERNATIONAL
(2022)
Article
Chemistry, Physical
Huiying Gao, Menglei Li, Yu Yang, Ping Zhang
Summary: First-principles calculations were used to study the structural, magnetic, and electronic properties of PuO2-xHx compounds in fluorite structure. Different density functional methods were applied to investigate the unique characteristics of the materials under various oxygen and hydrogen compositions. The results showed distinct lattice deformation and magnetic behaviors depending on the Pu and H content, with a transition from insulator to metal property observed within a specific range of x value.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Chemistry, Physical
Saveer Ahmad Khandy, Thamraa Alshahrani, H. I. Elsaeedy, Dinesh C. Gupta
Summary: In this study, the structural stability, elastic constants, electronic structures, and transport properties of Cs2GeMnI6 and Cs2GeNiI6 double perovskite structures were investigated using Density Functional Theory (DFT) and quantum mechanical calculations. The results showed promising properties for potential applications in spin-based and thermoelectric technologies.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Engineering, Electrical & Electronic
Saurabh Yadav, Amit Kumar Singh, M. K. Roy, Y. S. Katharria
Summary: The optical, structural, and dielectric properties of SnO2-Ga2O3 nanocomposites were studied. The addition of Sn in Ga2O3 significantly influenced the dielectric measurements. The dielectric constant and dielectric loss decreased, while the electrical conductivity increased with increasing Sn content.
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
(2023)
Article
Chemistry, Multidisciplinary
Jun-Rui Liu, Xiao-Ping Wei, Wen-Li Chang, Xiaoma Tao
Summary: Using first-principles calculations, the CrLaCoZ (Z = Al, Ga, In, Ge, Sn, Pb) Heusler alloys are predicted to be half-metals. The structural stability of these alloys is analyzed in terms of various factors, and it is found that CrLaCoAl, CrLaCoGa, CrLaCoIn, and CrLaCoSn are easier to synthesize experimentally. The formation of a half-metallic gap is attributed to the hybridization of d-d and p-d orbitals, while the presence of impurities destroys their half-metallicity. Additionally, the effects of spin-orbit coupling on electronic structure and the thermoelectric properties of these alloys are investigated.
JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS
(2022)
Article
Materials Science, Ceramics
Chen Wang, Shi-Wei Li, Wei-Hang Fan, Yu-Chao Zhang, Xiao-Ying Zhang, Rong-Rong Guo, Hai-Jun Lin, Shui-Yang Lien, Wen-Zhang Zhu
Summary: This study systematically investigated the evolution of Ga2O3 films deposited on Al2O3(0001) at different substrate temperatures using PLD. By standardizing the thickness of the films, the effect of substrate temperature on the film properties was explored, leading to the production of high-quality crystalline Ga2O3 films suitable for high-performance power electric devices and photoelectronic devices.
CERAMICS INTERNATIONAL
(2021)
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
Chemistry, Multidisciplinary
Kushal Rijal, Stephanie Amos, Pavel Valencia-Acuna, Fatimah Rudayni, Neno Fuller, Hui Zhao, Hartwin Peelaers, Wai-Lun Chan
Summary: Periodic nanoscale potentials can trap interlayer excitons by utilizing the structure deformability of a 2D molecular crystal as a degree of freedom. The PTCDI lattice on MoS2 creates a spatial variation of molecular orbital energy, providing effective trapping sites for IXs.
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
Nanoscience & Nanotechnology
Panpan Li, Hongjian Li, Yifan Yao, Norleakvisoth Lim, Matthew Wong, Mike Iza, Michael J. Gordon, James S. Speck, Shuji Nakamura, Steven P. DenBaars
Summary: We have shown a significant improvement in the quantum efficiency of InGaN red micro-light-emitting diodes (mu LEDs). The peak external quantum efficiency (EQE) of the packaged 80 x 80 mu m(2) InGaN red mu LEDs increased to 6.0% at 12A/cm(2), indicating a significant advancement in the efficiency exploration of InGaN red mu LEDs. The enhancement in EQE is attributed to improved quantum efficiency, confirmed by electron-hole wavefunction overlap and photoluminescence intensity ratio analysis. Additionally, ultrasmall 5x 5 mu m(2) InGaN red mu LEDs were obtained with a high peak EQE of 4.5%.
Article
Physics, Applied
Su-Hyun Yoo, Mira Todorova, Jorg Neugebauer, Chris G. Van de Walle
Summary: GaN/(Al, Ga)N heterojunctions are crucial for high-electron-mobility transistors. The density of the two-dimensional electron gas (2DEG) on the GaN side is significantly enhanced by the strong polarization fields at the interface. The source of the electrons in the 2DEG is intrinsic to the overall structure and the negative charge is balanced by fixed charge on the surface, rather than surface states.
PHYSICAL REVIEW APPLIED
(2023)
Article
Nanoscience & Nanotechnology
Takeki Itoh, Akhil Mauze, Yuewei Zhang, James S. Speck
Summary: Continuous Si doping in beta-Ga2O3 epitaxial films was achieved using plasma-assisted molecular beam epitaxy with a valved effusion cell for the Si source. Secondary ion mass spectroscopy results indicated flat and sharply turned Si doping profiles in beta-Ga2O3. The Si doping concentration could be controlled by adjusting the cell temperature or the valve aperture of the Si effusion cell. High crystal quality and smooth surface morphologies were observed in Si-doped beta-Ga2O3 films grown on (010) and (001) substrates. The Si-doped (001) beta-Ga2O3 epitaxial film exhibited an electron mobility of 67 cm(2)/Vs at a Hall concentration of 3 x 10(18) cm(-3).
Article
Quantum Science & Technology
Mehmet T. Uysal, Mouktik Raha, Songtao Chen, Christopher M. Phenicie, Salim Ourari, Mengen Wang, Chris G. Van de Walle, Viatcheslav V. Dobrovitski, Jeff D. Thompson
Summary: In this work, coherent coupling between the electron spin of a single Er3+ ion and a single I = 1/2 nuclear spin in the solid-state host crystal, which is a fortuitously located proton (1H), is demonstrated. The nuclear spin is controlled using dynamical-decoupling sequences applied to the electron spin, allowing for one- and two-qubit gate operations. The longer coherence time of the nuclear spin, compared to the electron spin, is crucial for combining long-lived nuclear spin quantum registers with telecom-wavelength emitters for long-distance quantum repeaters.
Article
Physics, Multidisciplinary
Fangzhou Zhao, Mark E. Turiansky, Audrius Alkauskas, Chris G. Van de Walle
Summary: Trap-assisted Auger-Meitner recombination is highlighted as a dominant nonradiative process in wide-band-gap materials, and a first-principles methodology is presented to determine the rates of this process in semiconductors or insulators due to defects or impurities.
PHYSICAL REVIEW LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Ymir K. Frodason, Joel B. Varley, Klaus Magnus H. Johansen, Lasse Vines, Chris G. Van de Walle
Summary: Pathways and energy barriers for the migration of Ga vacancies (VGa) and Ga interstitials (Gai) in-Ga2O3 have been studied using hybrid functional calculations and the nudged elastic band method. A mechanism for the transformation of VGa between different split configurations has been described. The overall migration barriers for VGa and Gai in different crystal directions have been determined. The results provide insights into the thermally activated recovery processes in irradiated material.
