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Fine structure splitting of isoelectronic bound excitons in nitrogen-doped GaAs

Physical Review B 2008年第19期77卷 193102-193102页

作者： Takashi Kita Yukihiro Harada Osamu Wada Department of Electrical and Electronics Engineering Graduate School of Engineering Kobe University Rokkodai 1-1 Nada Kobe 657-8501 Japan

We have studied the fine structure polarization splitting of exciton emission lines related to isoelectronic centers in an nitrogen-doped GaAs. The nitrogen doping has been performed in atomically controlled way using the (3×3) nitrogen stable surface of GaAs(001), which forms a series of distinct, strong, narrow bandwidth luminescence lines. The localized bound excitons have been found to consist of four signals, which can be selected by linear polarization. Magnetic-field-induced change in the splitting shows a quadratic dependence of the bright exciton splitting owing to the in-plane Zeeman interaction. Our calculations of the optical selection characteristics considering both the J−J coupling and local-field effects demonstrate the polarization splitting depending on the symmetry of the isoelectronic center.

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Area-I/O flip-chip routing for chip-package co-design 08

Area-I/O flip-chip routing for chip-package co-design

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IEEE International Conference on Computer-Aided Design

作者： Jia-Wei Fang Yao-Wen Chang Graduate Institute of Electronics Engineering National Taiwan University Taipei Taiwan Department of Electrical Engineering National Taiwan University Taipei Taiwan

ISBN: (纸本)9781424428205

The area-I/O flip-chip package provides a high chip-density solution to the demand of more I/Opsilas in VLSI designs; it can achieve smaller package size, shorter wirelength, and better signal and power integrity. In this paper, we introduce the routing problem for chip and package co-design and present the first work in the literature to handle the multiple Re-Distribution Layer (RDL) routing problem for flip-chip designs, considering pin and layer assignment, total wirelength minimization, and chip-package co-design. Our router adopts a two-stage technique of global routing followed by RDL routing. The global routing assigns each block port to a unique bump pad via an I/O pad and decides the RDL routing among I/O pads and bump pads. Based on the minimum-cost maximum-flow algorithm, we can guarantee 100% RDL routing completion after the assignment and the optimal solution with the minimum wirelength. The RDL routing efficiently distributes the routing points between two adjacent bump pads and then generates a 100% routable sequence to complete the routing. Experimental results based on 10 industry designs demonstrate that our router can achieve 100% routability and the optimal routing wirelength under reasonable CPU times, while related works cannot.

关键词： Routing electronics packaging Very large scale integration Design engineering Signal design Large-scale systems Joining processes Inductance

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Light scattering by white-emitting CdSe nanocrystals and traditional YAG:Ce3+ phosphor particles

Light scattering by white-emitting CdSe nanocrystals and tra...

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2008 MRS Fall Meeting

作者： Gosnell, Jonathan D. Weiss, Sharon M. Interdisciplinary Graduate Program in Materials Science Vanderbilt University Station B 350106 Nashville TN 37235 United States Department of Electrical Engineering and Computer Science Vanderbilt University Station B 351824 Nashville TN 37235 United States

ISBN: (纸本)9781615677740

In order for solid state lighting technology to become a mainstream technology, one of the major challenges to overcome is increasing the efficiency of these devices while maintaining a proper color balance. A significant source of efficiency loss in commercial phosphor-based white light-emitting diodes (LEDs) is light scattering off large, micron-sized phosphor particles. The use of recently reported single-size CdSe white-light nanocrystals in place of traditional phosphors, such as YAG:Ce3+, could lead to lower scattering losses and higher device efficiencies as a result of the extremely small CdSe core diameter of approximately 1.5 nm. This work theoretically and experimentally investigates the absorption, scattering, and extinction coefficients and cross sections of CdSe white-light nanocrystals in comparison to YAG:Ce3+ phosphor particles. Calculations were performed based on the Rayleigh approximation and Mie theory of scattering. Experiments were carried out using thin films of encapsulated nanocrystals. By measuring the absorbance and thickness of the films, in addition to the concentration of the nanocrystals, extinction coefficients and cross sections were determined using the Beer-Lambert law. A reasonable agreement was obtained between theoretical and experimental data showing that the size of the particle has a significant impact on the extinction, absorption, and scattering properties of thin films. The considerably reduced scattering from the nanocrystals compared to traditional phosphors, along with their inherent high quality white light emission, makes them a promising candidate for future solid state lighting applications. © 2009 Materials Research Society.

关键词： Cadmium compounds

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Double-Barrier Superlattice Infrared Photodetectors

Double-Barrier Superlattice Infrared Photodetectors

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IEEE Conference on Nanotechnology

作者： Shih-Hung Lin Ying-Hsiang Wang Jen-Hsiang Lu Chieh-Hsiung Kuan Juei-Yang Feng Tsong-Sheng Lay Department of Electrical Engineering and Graduate Institute of Electronics Engineering National Taiwan University Taipei Taiwan Graduate Institute of Electro-Optical Engineering National Sun Yat-Sen University Kaohsiung Taiwan

ISBN: (纸本)9781424421039

We have designed a double-barrier superlattice infrared photodetector (SLIP) which has a superlattice (SL) sandwiched between the thin and thick barriers. Photoelectrons can bounce back and forth between the two barriers and inject through the thin barrier to enhance the photocurrent. However, the supply of electrons is limited by the thick barrier and thus we have to fabricate the emitter contact on the SL. In comparison with the single-barrier SLIP, this structure shows at least one-order higher magnitude of photocurrent at low bias and the associated detectivity is also increased for more than one order. The dramatic increment of the photocurrent is consistent with our design in the detailed analysis. Because it has the optimized performance at low bias, this double-barrier SLIP is suitable for low power consumption applications. Our detector can be operated at 100 K by blocking barriers incorporated into the structure to reduce the dark current.

关键词： Detectors Photoconductivity Dark current Photodetectors Superlattices Arrays Electric fields

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Post fabrication electric field treatment of polymer light emitting and photovoltaic devices

Post fabrication electric field treatment of polymer light e...

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Ph.D. Research in Microelectronics and electronics (PRIME)

作者： Ali Osman Sevim Senol Mutlu System and Control Engineering Institute for Graduate Studies in Sciences and Engineering Bogazici University Istanbul Turkey Department of Electrical and Electronics Engineering College of Engineering Bogazici University Istanbul Turkey

ISBN: (纸本)9781424419838

Conjugated polymers are semiconductors that offer flexibility, simplicity and lower cost in the fabrication of polymer light emitting diodes (PLEDs), polymer transistors and circuits, polymer photodetectors and solar cells. They have a potential to lead to a technology that can monolithically integrate all the semiconductor devices mentioned above as well as polymer sensors and actuators. This paper presents a novel method as a post-fabrication treatment and its improvements over the performance of the light emitting and photovoltaic properties of PLEDs. Investigated PLED is made of indium tin oxide (ITO), poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS), poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and aluminum (Al). Following fabrication at room conditions, heat treatment is performed at 130Cdeg for one hour and electric field treatment is realized with voltage levels from 0 to -8 V under 0.2 atm vacuum. Heat treatment after fabrication restores the light emitting function of otherwise not functioning PLEDs, which degrade due to exposure to oxygen and water vapors at normal room conditions. Electric field treatment reduces the turn-on voltage of PLEDs when they are used as light emitting devices. Electric field treatment of -1 volt reduces the turn-on voltage to 3 volts from 10 volts, which is the case for the devices with heat treatment only. It also improves open circuit voltages and short circuit currents of PLEDs by an order of magnitude when they are used as photo-detectors or photocells. Devices treated with heat only show a short circuit current of around 0.5 nA and open circuit voltage of 5 mV under 500 mW/m 2 light intensity. These values improve to 5 nA and 55 mV respectively after the devices are electrically treated with -1 volt. Electric field treatment after the thermal treatment also improves the stability and uniformity of the devices.

关键词： Electric fields Polymers Fabrication Heat treatment Resistance heating Photovoltaic systems Solar power generation

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A 100 MHz 1920×1080 HD-Photo 20 frames/sec JPEG XR encoder design

A 100 MHz 1920×1080 HD-Photo 20 frames/sec JPEG XR encoder ...

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IEEE International Conference on Image Processing

作者： Ching-Yen Chien Sheng-Chieh Huang Shih-Hsiang Lin Yu-Chieh Huang Yi-Cheng Chen Lei-Chun Chou Tzu-Der Chuang Yu-Wei Chang Chia-Ho Pan Liang-Gee Chen Sense/TCM SOC Lab Department of Electrical and Control Engineering National Chiao Tung University Hsinchu Taiwan Graduate Institute of Electronics Engineering and Department of Electrical Engineering National Taiwan University Taipei Taiwan

A JPEG XR chip for HD-Photo is implemented with 25 mm 2 area in TSMC 0.18 um CMOS 1P6M technology at 100 MHz. According to the simulation results, the 4:4:4 1920x1080 HD-Photo 20 frames/sec can be encoded smoothly.

关键词： Image coding Tiles Transform coding CMOS technology Displays Quantization Airplanes Control engineering Design engineering Electronic mail

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Effect of pressure on electromechanical properties for PMN-PT ceramics with compositions near morphotropic phase boundary

Effect of pressure on electromechanical properties for PMN-P...

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作者： Yasuda, Naohiko Ozawa, Koichi Rahaman, Md. M. Ohwa, Hidehiro Yamashita, Yohachi Iwata, Makoto Ishibashi, Yoshihiro Electrical and Electronic Engineering Department Gifu University Gifu 501-1193 Japan Corporate R and D Center Toshiba Corporation Saiwai-ku Kawasaki 212-8582 Japan Department of Engineering Physics Electronics and Mechanics Graduate School of Engineering Nagoya Institute of Technology Nagoya 466-8555 Japan Faculty of Business Aichi Shukutoku University Nagakute-cho Aichi 480-1197 Japan

The piezoelectric properties of PMN-PT ceramics with compositions near a morphotropic phase boundary were investigated under pressures p upto 150 MPa. The resonance and antiresonance frequency characteristics of impedance and phase in the k31mode in the tetragonal phase for PMNT (67/33) and in the rhombohedral one for PMNT (69/31) ceramics were observed under various pressures. The resonance frequency fr remains almost constant and antiresonance one fa tends to increase with increasing p. The electromechanical coupling coefficient k31 in the k31 mode increases and the electromechanical quality factor Q decreases with increasing p. The decrease in Q with p is due to ferroelectric domain wall motions. The relative permittivity r increases with increasing p. Such an increase in both k and Εr dependent on p seems to be related to the decrease in ferroelectric domain size.

关键词： Permittivity

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Fluidity concept for NoC: A congestion avoidance and relief routing scheme

Fluidity concept for NoC: A congestion avoidance and relief ...

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IEEE International SOC Conference

作者： Ying-Cherng Lan Michael C. Chen Alan P. Su Yu-Hen Hu Sao-Jie Chen Graduate Institute of Electronics Engineering National Taiwan University Taipei Taiwan SpringSoft Inc. Department of Electrical and Computer Engineering University of Wisconsin WI USA Graduate Institute of Electrical Engineering National Taiwan University Taipei Taiwan

ISBN: (纸本)9781424425969

In this paper, we utilize a novel fluidity concept to analyze and develop routing algorithms in network-on-chip for congestion avoidance and relief. We develop a new model to capture congestion information which improves the performance of routing algorithms. Comparisons of algorithms using our model consistently outperform the original algorithms themselves.

关键词： Routing Algorithm design and analysis Traffic control Delay Fluids Heuristic algorithms System-on-a-chip

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Znic Oxide Nanowires with Ultra-Thin and Low-Resistance Seed Layer

Znic Oxide Nanowires with Ultra-Thin and Low-Resistance Seed...

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IEEE Conference on Nanotechnology

作者： Wen-Yan Su Ching-Fuh Lin Graduate Institute of Photonics and Optoelectronics National Taiwan University Taipei Taiwan Graduate Institute of Photonics and Optoelectronics Graduate Institute of Electronics Engineering and Department of Electrical Engineering National Taiwan University Taiwan

ISBN: (纸本)9781424421039

We report the zinc oxide (ZnO) nanowires with ultra-thin seed layer by low-cost hydrothermal method. The ultra-thin seed layer consists of ZnO thin film, which is fabricated by sol-gel method and then etched to reduce the thickness by diluted HCI. The resistance along the vertical direction of the ultra-thin seed layer on the indium tin oxide (ITO) glass decreases during the etching process. ZnO nanowires with low resistance in the vertical direction are expected to enable the application of optoelectronic device with better performance.

关键词： Zinc oxide Nanowires Indium tin oxide Films Resistance Glass Substrates

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Frame rate up-conversionwith global-to-local iterative motion compensated interpolation

Frame rate up-conversionwith global-to-local iterative motio...

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IEEE International Conference on Multimedia and Expo (ICME)

作者： Kung-Yen Hsu Shao-Yi Chien Media IC and System Laboratory Graduate Institute of Electronics Engineering and Department of Electrical Engineering National Taiwan University of Science and Technology Taipei Taiwan

Video frame rate up conversion (FRUC) has many applications, especially it has been proved to effectively reduce the motion blur problem and improve the visual quality on LCD. In this paper, we propose a global-to-local iterative algorithm to resolve the problems occurring in the existing block based algorithms. In addition, the iterative approach, where interpolated blocks are generated in confident order, is employed in order to find the applying order and combination of different motion compensated interpolation(MCI) algorithms. Experimental results show that the proposed algorithm outperforms other MCI algorithms in perceptual and can generate smooth high quality interpolated frames.

关键词： Interpolation Classification algorithms Correlation Pixel Jitter Strontium PSNR

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