scholarly journals Recent Advances in Fabricating Wurtzite AlN Film on (0001)-Plane Sapphire Substrate

Crystals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 38
Author(s):  
Hualong Wu ◽  
Kang Zhang ◽  
Chenguang He ◽  
Longfei He ◽  
Qiao Wang ◽  
...  
Keyword(s):  
Sapphire Substrate ◽  
Frequency Comb ◽  
Optical Nonlinearity ◽  
Crystalline Quality ◽  
Bulk Acoustic Wave ◽  
Threading Dislocation ◽  
High Electron ◽  
Recent Advances ◽  
Aln Film ◽  
The Future

Ultrawide bandgap (UWBG) semiconductor materials, with bandgaps far wider than the 3.4 eV of GaN, have attracted great attention recently. As a typical representative, wurtzite aluminum nitride (AlN) material has many advantages including high electron mobility, high breakdown voltage, high piezoelectric coefficient, high thermal conductivity, high hardness, high corrosion resistance, high chemical and thermal stability, high bulk acoustic wave velocity, prominent second-order optical nonlinearity, as well as excellent UV transparency. Therefore, it has wide application prospects in next-generation power electronic devices, energy-harvesting devices, acoustic devices, optical frequency comb, light-emitting diodes, photodetectors, and laser diodes. Due to the lack of low-cost, large-size, and high-ultraviolet-transparency native AlN substrate, however, heteroepitaxial AlN film grown on sapphire substrate is usually adopted to fabricate various devices. To realize high-performance AlN-based devices, we must first know how to obtain high-crystalline-quality and controllable AlN/sapphire templates. This review systematically summarizes the recent advances in fabricating wurtzite AlN film on (0001)-plane sapphire substrate. First, we discuss the control principles of AlN polarity, which greatly affects the surface morphology and crystalline quality of AlN, as well as the electronic and optoelectronic properties of AlN-based devices. Then, we introduce how to control threading dislocations and strain. The physical thoughts of some inspirational growth techniques are discussed in detail, and the threading dislocation density (TDD) values of AlN/sapphire grown by various growth techniques are compiled. We also introduce how to achieve high thermal conductivities in AlN films, which are comparable with those in bulk AlN. Finally, we summarize the future challenge of AlN films acting as templates and semiconductors. Due to the fast development of growth techniques and equipment, as well as the superior material properties, AlN will have wider industrial applications in the future.

A Dynamic Systems Approach to Personality

2001 ◽  
Vol 6 (3) ◽  
pp. 172-176 ◽  
Author(s):  
Lawrence A. Pervin
Keyword(s):  
Dynamic Systems ◽  
Systems Approach ◽  
Biological Processes ◽  
Recent Advances ◽  
Dynamic View ◽  
The Future ◽  
History Of

David Magnusson has been the most articulate spokesperson for a holistic, systems approach to personality. This paper considers three concepts relevant to a dynamic systems approach to personality: dynamics, systems, and levels. Some of the history of a dynamic view is traced, leading to an emphasis on the need for stressing the interplay among goals. Concepts such as multidetermination, equipotentiality, and equifinality are shown to be important aspects of a systems approach. Finally, attention is drawn to the question of levels of description, analysis, and explanation in a theory of personality. The importance of the issue is emphasized in relation to recent advances in our understanding of biological processes. Integrating such advances into a theory of personality while avoiding the danger of reductionism is a challenge for the future.

Recent advances in sustainable production and catalytic transformations of fatty acid methyl esters

2021 ◽  
Author(s):  
Artem S. Belousov ◽  
Anton Esipovich ◽  
Evgeny Kanakov ◽  
Ksenia V. Otopkova
Keyword(s):  
Fatty Acid ◽  
Green Chemistry ◽  
Fatty Acid Methyl Esters ◽  
Methyl Esters ◽  
Environmental Issues ◽  
Sustainable Production ◽  
Catalytic Transformations ◽  
Acid Methyl ◽  
Recent Advances ◽  
The Future

Living in the time of the most heighten environmental issues, humanity should take care about the future. Green Chemistry provides a broad range of possibilities for researchers to design of...

scholarly journals Recent advances in organosolv fractionation: Towards biomass fractionation technology of the future

2020 ◽  
Vol 306 ◽  
pp. 123189 ◽  
Author(s):  
Petter Paulsen Thoresen ◽  
Leonidas Matsakas ◽  
Ulrika Rova ◽  
Paul Christakopoulos
Keyword(s):  
Recent Advances ◽  
Biomass Fractionation ◽  
The Future

scholarly journals Challenges and Techniques for Simulating Line Emission

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 100 ◽  
Author(s):  
Karen Olsen ◽  
Andrea Pallottini ◽  
Aida Wofford ◽  
Marios Chatzikos ◽  
Mitchell Revalski ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Emission Line ◽  
Line Emission ◽  
Emission Lines ◽  
Synthetic Spectra ◽  
Recent Advances ◽  
The Future ◽  
Important Quality ◽  
Circumgalactic Medium

Modeling emission lines from the millimeter to the UV and producing synthetic spectra is crucial for a good understanding of observations, yet it is an art filled with hazards. This is the proceedings of “Walking the Line”, a 3-day conference held in 2018 that brought together scientists working on different aspects of emission line simulations, in order to share knowledge and discuss the methodology. Emission lines across the spectrum from the millimeter to the UV were discussed, with most of the focus on the interstellar medium, but also some topics on the circumgalactic medium. The most important quality of a useful model is a good synergy with observations and experiments. Challenges in simulating line emission are identified, some of which are already being worked upon, and others that must be addressed in the future for models to agree with observations. Recent advances in several areas aiming at achieving that synergy are summarized here, from micro-physical to galactic and circum-galactic scale.

Silane controlled three dimensional GaN growth and recovery stages on a cone-shape nanoscale patterned sapphire substrate by MOCVD

CrystEngComm ◽  
2015 ◽  
Vol 17 (24) ◽  
pp. 4469-4474 ◽  
Author(s):  
J. Z. Li ◽  
Z. Z. Chen ◽  
Q. Q. Jiao ◽  
Y. L. Feng ◽  
S. Jiang ◽  
...  
Keyword(s):  
Sapphire Substrate ◽  
Strain Relaxation ◽  
Three Dimensional ◽  
Crystalline Quality ◽  
High Crystalline Quality ◽  
Patterned Sapphire Substrate ◽  
Specular Surface

The silane-controlled 3D growth led to a high crystalline quality, much strain relaxation and a specular surface for the GaN epilayers on NPSS.

High Voltage AlGaN/GaN Heterojunction Transistors

2004 ◽  
Vol 14 (01) ◽  
pp. 225-243 ◽  
Author(s):  
L. S. McCarthy ◽  
N-Q. Zhang ◽  
H. Xing ◽  
B. Moran ◽  
S. DenBaars ◽  
...  
Keyword(s):  
Drain Current ◽  
Gate Insulator ◽  
Threading Dislocation ◽  
High Electron ◽  
Resistive Load ◽  
Power Switching ◽  
Field Plate ◽  
Switching Power ◽  
Dislocation Densities ◽  
Extrinsic Base

The use of AlGaN / GaN HEMTs and HBTs for switching power supplies is explored. With its high electron velocities and breakdown fields, GaN has great potential for power switching. The field-plate HEMT increased breakdown voltages by 20% to 570V by reducing the peak field at the drain-side edge of the gate. The use of a gate insulator is also investigated, using both JVD SiO 2 and e-beam evaporated SiO 2 to reduce gate leakage, increasing breakdown voltages to 1050V and 1300V respectively. The power device figure of merit (FOM) for these devices: [Formula: see text], is the highest reported for switching devices. To reduce trapping effects, reactively sputtered SiN x, is used as a passivant, resulting in a switching time of less than 30 ns for devices blocking over 110V with a drain current of 1.4A under resistive load conditions. Dynamic load results are also presented. The development of HBTs for switching applications included the development of an etched emitter HBT with a selectively regrown extrinsic base. This was later improved upon with the selectively regrown emitter devices with current gains as high as 15. To improve breakdown in these devices, thick GaN layers were grown, reducing threading dislocation densities in the active layers. A further improvement included the use of a bevelled shallow etch and a lateral collector design to maximize device breakdown.

Conclusions: Recent Advances and the Future Prospects of the Lake Skadar/Shkodra Environment

2018 ◽  
pp. 481-500 ◽  
Author(s):  
Vladimir Pešić ◽  
Gordan S. Karaman ◽  
Andrey G. Kostianoy ◽  
Vesna Vukašinović-Pešić
Keyword(s):  
Future Prospects ◽  
Recent Advances ◽  
The Future ◽  
Lake Skadar

Rehabilitation Systems in Ambient Assisted Living Environments

2015 ◽  
pp. 60-78
Author(s):  
A. M. Middleton ◽  
R. P. Harte ◽  
T. E. Ward
Keyword(s):  
Research And Development ◽  
Motion Capture ◽  
Assisted Living ◽  
Serious Games ◽  
Ambient Assisted Living ◽  
Robotic Rehabilitation ◽  
Recent Advances ◽  
The Future ◽  
Living Environments

This chapter reviews Ambient Assisted Living (AAL) in the context of movement-based rehabilitation. The authors analyse the need for AAL solutions and how they can overcome many of the drawbacks associated with traditional rehabilitation. They discuss the benefits and challenges of rehabilitation within the AAL paradigm and the well-known benefits that the telerehabilitation and telemedicine models have already established. The authors review the top ambient technologies in use today, detailing their advantages and shortcomings. The review focuses primarily on areas such as motion capture, serious games, and robotic rehabilitation. The authors carry out a structured search of two well-known databases to find the most recent advances and present the most interesting lines of research and development. Finally, the authors discuss the review findings and draw conclusions on the future of personalised rehabilitation within an AAL paradigm.

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