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Jeffrey Y. Tsao

Bio: Jeffrey Y. Tsao is an academic researcher from Sandia National Laboratories. The author has contributed to research in topics: Solid-state lighting & Molecular beam epitaxy. The author has an hindex of 35, co-authored 151 publications receiving 6821 citations. Previous affiliations of Jeffrey Y. Tsao include Cornell University & United States Department of Energy.


Papers
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Journal ArticleDOI
TL;DR: The UWBG semiconductor materials, such as high Al‐content AlGaN, diamond and Ga2O3, advanced in maturity to the point where realizing some of their tantalizing advantages is a relatively near‐term possibility.
Abstract: J. Y. Tsao,* S. Chowdhury, M. A. Hollis,* D. Jena, N. M. Johnson, K. A. Jones, R. J. Kaplar,* S. Rajan, C. G. Van de Walle, E. Bellotti, C. L. Chua, R. Collazo, M. E. Coltrin, J. A. Cooper, K. R. Evans, S. Graham, T. A. Grotjohn, E. R. Heller, M. Higashiwaki, M. S. Islam, P. W. Juodawlkis, M. A. Khan, A. D. Koehler, J. H. Leach, U. K. Mishra, R. J. Nemanich, R. C. N. Pilawa-Podgurski, J. B. Shealy, Z. Sitar, M. J. Tadjer, A. F. Witulski, M. Wraback, and J. A. Simmons

785 citations

Journal ArticleDOI
TL;DR: In this paper, a model for the relaxation of an initially coherent metastable strained layer is developed, which is applied to relief of mismatch strain in the SiGe/Si(100) system, and good agreement with experimental data is found.
Abstract: An outstanding puzzle concerning strained‐layer semiconductors is that metastable structures can be grown in which exact coherence with the lattice is apparently conserved in layers much thicker than the equilibrium critical thickness. Using standard descriptions of dislocation dynamics and relaxation via plastic flow, a model for the relaxation of an initially coherent metastable strained layer is developed. This model is applied to relief of mismatch strain in the SiGe/Si(100) system, and good agreement with experimental data is found. Furthermore, the combined effect of relaxation kinetics and finite instrumental resolution on the observed critical thickness was calculated. The results successfully reproduce experimental data on metastable critical thickness in the SiGe/Si(100) system.

492 citations

Journal ArticleDOI
TL;DR: In this article, the authors compared the performance of LEDs and blue laser diode (LD) for future solid-state lighting (SSL) systems and compared their current state-of-the-art input-power-density-dependent power-conversion efficiencies and potential improvements both in their peak powerconversion efficiency and in the input power densities at which those efficiencies peak.
Abstract: Solid-state lighting (SSL) is now the most efficient source of high color quality white light ever created. Nevertheless, the blue InGaN light-emitting diodes (LEDs) that are the light engine of SSL still have significant performance limitations. Foremost among these is the decrease in efficiency at high input current densities widely known as “efficiency droop.” Efficiency droop limits input power densities, contrary to the desire to produce more photons per unit LED chip area and to make SSL more affordable. Pending a solution to efficiency droop, an alternative device could be a blue laser diode (LD). LDs, operated in stimulated emission, can have high efficiencies at much higher input power densities than LEDs can. In this article, LEDs and LDs for future SSL are explored by comparing: their current state-of-the-art input-power-density-dependent power-conversion efficiencies; potential improvements both in their peak power-conversion efficiencies and in the input power densities at which those efficiencies peak; and their economics for practical SSL.

434 citations

Journal ArticleDOI
TL;DR: In this article, the authors give a brief historical and forward-looking overview of conventional and SSL lighting technologies, and describe some of the simplest but most important lamp, chip, and materials design choices that will need to be made.
Abstract: The aim of this article is twofold. First, we give a brief historical and forward-looking overview of conventional and SSL lighting technologies. We focus on SSL technology based on inorganic light-emitting diodes (SSL-LEDs), rather than that based on organic light-emitting diodes (SSL-OLEDs), as SSL-LED technology is more advanced and more likely to be first to enter general illumination applications. Second, we describe some of the simplest but most important lamp, chip, and materials design choices that will need to be made. We especially focus on the constraints imposed on those design choices if SSL-LED technology is to fulfill its promise for general illumination.

418 citations

Book
01 Jan 1992
TL;DR: In this paper, the authors present a list of figures and tables for Free Energies and Open Systems, including the following: Figure 1: Surface Morphology and Composition; Figure 2: Surface Composition.
Abstract: Preface. List of Figures. List of Tables. Bulk Phase Equilibra. Free Energies and Open Systems. Elemental Phases. Alloy Phases. Thin Film Structure and Microstructure. Ordering and Clustering. Coherency and Semi-coherency. Surface Morphology and Composition. Surface Composition. Index.

418 citations


Cited by
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Journal Article
TL;DR: Prospect Theory led cognitive psychology in a new direction that began to uncover other human biases in thinking that are probably not learned but are part of the authors' brain’s wiring.
Abstract: In 1974 an article appeared in Science magazine with the dry-sounding title “Judgment Under Uncertainty: Heuristics and Biases” by a pair of psychologists who were not well known outside their discipline of decision theory. In it Amos Tversky and Daniel Kahneman introduced the world to Prospect Theory, which mapped out how humans actually behave when faced with decisions about gains and losses, in contrast to how economists assumed that people behave. Prospect Theory turned Economics on its head by demonstrating through a series of ingenious experiments that people are much more concerned with losses than they are with gains, and that framing a choice from one perspective or the other will result in decisions that are exactly the opposite of each other, even if the outcomes are monetarily the same. Prospect Theory led cognitive psychology in a new direction that began to uncover other human biases in thinking that are probably not learned but are part of our brain’s wiring.

4,351 citations

Journal ArticleDOI
27 May 2005-Science
TL;DR: The high efficiency of solid-state sources already provides energy savings and environmental benefits in a number of applications, but these sources also offer controllability of their spectral power distribution, spatial distribution, color temperature, temporal modulation, and polarization properties.
Abstract: More than a century after the introduction of incandescent lighting and half a century after the introduction of fluorescent lighting, solid-state light sources are revolutionizing an increasing number of applications. Whereas the efficiency of conventional incandescent and fluorescent lights is limited by fundamental factors that cannot be overcome, the efficiency of solid-state sources is limited only by human creativity and imagination. The high efficiency of solid-state sources already provides energy savings and environmental benefits in a number of applications. However, solid-state sources also offer controllability of their spectral power distribution, spatial distribution, color temperature, temporal modulation, and polarization properties. Such ‘‘smart’’ light sources can adjust to specific environments and requirements, a property that could result in tremendous benefits in lighting, automobiles, transportation, communication, imaging, agriculture, and medicine.

3,164 citations

Journal ArticleDOI
TL;DR: In this paper, it is shown that very large stresses may be present in the thin films that comprise integrated circuits and magnetic disks and that these stresses can cause deformation and fracture to occur.
Abstract: The mechanical properties of thin films on substrates are described and studied. It is shown that very large stresses may be present in the thin films that comprise integrated circuits and magnetic disks and that these stresses can cause deformation and fracture to occur. It is argued that the approaches that have proven useful in the study of bulk structural materials can be used to understand the mechanical behavior of thin film materials. Understanding the mechanical properties of thin films on substrates requires an understanding of the stresses in thin film structures as well as a knowledge of the mechanisms by which thin films deform. The fundamentals of these processes are reviewed. For a crystalline film on a nondeformable substrate, a key problem involves the movement of dislocations in the film. An analysis of this problem provides insight into both the formation of misfit dislocations in epitaxial thin films and the high strengths of thin metal films on substrates. It is demonstrated that the kinetics of dislocation motion at high temperatures are expecially important to the understanding of the formation of misfit dislocations in heteroepitaxial structures. The experimental study of mechanical properties of thin films requires the development and use of nontraditional mechanical testing techniques. Some of the techniques that have been developed recently are described. The measurement of substrate curvature by laser scanning is shown to be an effective way of measuring the biaxial stresses in thin films and studying the biaxial deformation properties at elevated temperatures. Submicron indentation testing techniques, which make use of the Nanoindenter, are also reviewed. The mechanical properties that can be studied using this instrument are described, including hardness, elastic modulus, and time-dependent deformation properties. Finally, a new testing technique involving the deflection of microbeam samples of thin film materials made by integrated circuit manufacturing methods is described. It is shown that both elastic and plastic properties of thin film materials can be measured using this technique.

2,347 citations