Showing papers in "IEEE\/OSA Journal of Display Technology in 2013"
TL;DR: In this article, the effects of polarization-related electric fields on the energy band diagrams, wavelength shift, wave function overlap, and efficiency droop for InGaN quantum wells on various crystal orientations, including polar (0001) (c -plane), semipolar (2021), nonpolar (1010) (m-plane).
Abstract: This work examines the effects of polarization-related electric fields on the energy band diagrams, wavelength shift, wave function overlap, and efficiency droop for InGaN quantum wells on various crystal orientations, including polar (0001) (c -plane), semipolar (2021), semipolar (2021), and nonpolar (1010) (m-plane). Based on simulations, we show that the semipolar (2021) orientation exhibits excellent potential for the development of high-efficiency, low-droop light-emitting diodes (LEDs). We then present recent advancements in crystal growth, optical performance, and thermal performance of semipolar (2021) LEDs. Finally, we demonstrate a low-droop, high-efficiency single-quantum-well blue semipolar (2021) LED with an external quantum efficiency of more than 50% at 100 A/cm2.
317 citations
TL;DR: In this paper, a self-consistent 6-band k ·p method is used to calculate the band structure for InGaN QW structure and the analysis is based on current continuity relation for drift and diffusion carrier transport across the QW-barrier systems.
Abstract: Current injection efficiency and internal quantum efficiency (IQE) in InGaN quantum well (QW) based light emitting diodes (LEDs) are investigated. The analysis is based on current continuity relation for drift and diffusion carrier transport across the QW-barrier systems. A self-consistent 6-band k ·p method is used to calculate the band structure for InGaN QW structure. Carrier-photon rate equations are utilized to describe radiative and non-radiative recombination in the QW and the barrier regions, carrier transport and capture time, and thermionic emission leading to carrier leakage out of the QW. Our model indicates that the IQE in the conventional 24-A In0.28Ga0.72 N -GaN QW structure reaches its peak at low injection current density and reduces gradually with further increase in current due to the large thermionic carrier leakage. The efficiency droop phenomenon at high current density in III-nitride LEDs is thus consistent with the high-driving-current induced quenching in current injection efficiency predicted by our model. The effects of the monomolecular recombination coefficient, Auger recombination coefficient and GaN hole mobility on the current injection efficiency and IQE are studied. Structures combining InGaN QW with thin larger energy bandgap barriers such as AlxGa1-xN, lattice-matched AlxIn1-xN, and lattice-matched AlxInyGa1-x-y N have been analyzed to improve current injection efficiency and thus minimize droop at high current injection in III-nitride LEDs. Effect of the thickness of the larger energy bandgap barriers (AlGaN, AlInN and AlInGaN) on injection efficiency and IQE are investigated. The use of thin AlGaN barriers shows slight reduction of quenching of the injection efficiency as the current density increases. The use of thin lattice-matched AlInN or AlInGaN barriers shows significant suppression of efficiency-droop in nitride LEDs.
181 citations
TL;DR: In this paper, the band structure of dilute-As GaNAs alloy with the As composition range from 0% to 12.5% is studied by using First-Principle density-functional calculation.
Abstract: The band structure of dilute-As GaNAs alloy with the As composition range from 0% to 12.5% is studied by using First-Principle density-functional calculation. Our analysis shows that the dilute-As GaNAs alloy exhibits the direct band gap properties. The dilute-As GaNAs alloy shows a band gap range from 3.645 eV down to 2.232 eV with As content varying from 0% to 12.5%, which covers the blue and green spectral regime. This finding indicates the alloy as a potential candidate for photonic devices applications. The bowing parameter of 14.5 eV ±0.5 eV is also obtained using line fitting with the First-Principle and experimental data. The effective masses for electrons and holes in dilute-As GaNAs alloy, as well as the split-off energy parameters, were also presented. Minimal interband Auger recombination is also suggested for the dilute-As GaNAs alloy attributing to the off-resonance condition for this process.
104 citations
TL;DR: In this paper, the improvement of light extraction efficiency of InGaN light-emitting diodes (LEDs) using microsphere arrays with various refractive indices was analyzed.
Abstract: The improvement of light extraction efficiency of InGaN light-emitting diodes (LEDs) using microsphere arrays with various refractive indices was analyzed. Finite-difference time-domain (FDTD) simulations show that the use of microsphere (dmicrosphere = 500 nm) arrays with refractive indices of 1.8 and 2.5 led to increase in light extraction efficiency of InGaN LEDs by 1.9 times and 2.2 times, respectively. The enhancement in light extraction efficiency is attributed to the decrease in the Fresnel reflection and increase in effective photon escape cone due to graded refractive index and curvature formed between microsphere and free space. The maximum enhancement of light extraction efficiency of InGaN quantum well LEDs was achieved by employing the refractive index matched anatase-TiO2 microsphere arrays. The effects of microsphere diameters on the light extraction efficiency were also investigated and 2.4 times enhancement was achieved by employing 400-nm refractive index matched TiO2 sphere arrays.
98 citations
TL;DR: A detailed overview of the state-of-the-art white OLED design concepts including their working principles will be presented and a brief overview on the current status of out-coupling techniques suitable for white OLEDs will also be discussed.
Abstract: Lighting consumes a significant amount of generated electrical power in developing countries, and it uses over 20% of the energy supplied in developed countries. Therefore, semiconductor-based light sources with high energy efficiencies are critical technologies for the reduction of global carbon footprint. As an emerging lighting technology, organic light-emitting diode (OLED) has received huge worldwide attention in recent years, partially driven by its success in the flat-panel display market and partially driven by its technology virtues such as an unique thin, flat, foldable form factor. In this review, we will provide an overview on the current status of OLEDs for lighting applications. Specifically, a detailed overview of the state-of-the-art white OLED design concepts including their working principles will be presented. A brief overview on the current status of out-coupling techniques suitable for white OLEDs will also be discussed.
89 citations
TL;DR: In this article, the enhancement of light extraction efficiency of InGaN quantum well light emitting diodes (LEDs) was achieved by employing the refractive index matched microsphere arrays.
Abstract: The enhancement of light extraction efficiency of InGaN quantum well light emitting diodes (LEDs) was achieved by employing the refractive index matched ${\hbox{TiO}}_{2}$ microsphere arrays. The optimization studies of the dipping method and rapid convective deposition (RCD) method were carried out for the deposition of ${\hbox{TiO}}_{2}$ microsphere arrays onto LEDs. The two-dimensional (2D) close-packed ${\hbox{TiO}}_{2}$ microsphere arrays were deposited by the using optimized conditions of the dipping and RCD methods, respectively. The light extraction efficiencies of LEDs under electrical injection were enhanced by 1.8–1.9 times by utilizing 520-nm diameter amorphous and anatase ${\hbox{TiO}}_{2}$ microspheres via the two deposition methods.
88 citations
TL;DR: In this paper, the authors describe the design and fabrication of 360 PPI flip-chip mounted active matrix (AM) addressable light emitting diode on silicon (LEDoS) micro-displays.
Abstract: In this paper, we describe the design and fabrication of 360 PPI flip-chip mounted active matrix (AM) addressable light emitting diode on silicon (LEDoS) micro-displays. The LEDoS micro-displays are self-emitting devices which have higher light efficiency than liquid crystal based displays (LCDs) and longer lifetime than organic light emitting diodes (OLEDs) based displays . The LEDoS micro-displays were realized by integrating monolithic LED micro-arrays and silicon-based integrated circuit using a flip-chip bonding technique. The active matrix driving scheme was designed on the silicon to provide sufficient driving current and individual controllability of each LED pixel. Red, green, blue and Ultraviolet (UV) LEDoS micro-displays with a pixel size of 50 μm and pixel pitch of 70 μm were demonstrated. With a peripheral driving board, the LEDoS micro-display panels were programmed to show representative images and animations.
84 citations
TL;DR: In this paper, a glass phosphor layer with ultra-high thermal stability appropriate for phosphor-converted white light-emitting diodes (PC-WLEDs) is demonstrated.
Abstract: A glass phosphor layer with ultra-high thermal stability appropriate for phosphor-converted white light-emitting diodes (PC-WLEDs) is demonstrated. The results showed PC-WLEDs utilizing the high thermal stable glass phosphor maintained good thermal stability in lumen, chromaticity, and transmittance characteristics under the thermal aging condition up to 350 $^{\circ}{\hbox{C}}$ . This is a considerable high operating temperature for a phosphor layer in the PC-WLEDs. The lumen degradation, chromaticity shift, and transmittance loss in the glass-based PC-WLEDs under thermal aging at 150 $^{\circ}{\hbox{C}}$ , 250 $^{\circ}{\hbox{C}}$ , 350 $^{\circ}{\hbox{C}}$ , and 450 $^{\circ}{\hbox{C}}$ are also presented and compared with those of silicone-based PC-WLEDs under thermal aging at 150 $^{\circ}{\hbox{C}}$ and 250 $^{\circ}{\hbox{C}}$ . The result clearly demonstrated that the glass-based PC-WLEDs exhibited better thermal stability in lumen degradation, chromaticity shift, and transmittance loss than the silicone-based PC-WLEDs. The advantages of glass encapsulation in high-temperature operation of the PC-WLEDs could be explained that the glass transition temperature of the glass phosphor (567 $ ^{\circ}{\hbox{C}}$ ) was much higher than it of silicone (150 $ ^{\circ}{\hbox{C}}$ ). The newly developed ultra-high thermal-stable glass is essentially critical to the application of LED modules in the area where the high-power, high-temperature and absolute reliability are required for use in the next-generation solid-state lighting.
79 citations
TL;DR: In this article, the negative dielectric anisotropy (Δe) liquid crystal for fringing field switching (n-FFS) display was compared with positive and negative Δe liquid crystal.
Abstract: We report a high performance negative dielectric anisotropy (Δe) liquid crystal for fringing field switching (n-FFS) display. We compare the electro-optic characteristics of FFS cells using positive and negative Δe LCs. With comparable driving voltage and response time, the n-FFS cell has advantages in higher transmittance, single gamma curve, less cell gap sensitivity and slightly wider viewing angle. LC director deformation distribution is analyzed to explain these performance differences.
76 citations
TL;DR: It is shown that optical losses in the LED dictate light extraction, and that volumetric LEDs offer an opportunity for ultimate efficiency.
Abstract: Surface roughening is frequently employed to increase light extraction from light-emitting diodes (LEDs), especially in the important case of III-Nitride LEDs. We explore the physics governing this scheme. We introduce a numerical model, based on solving Maxwell's equations, to accurately describe scattering by a roughened semiconductor interface. This model reveals the complex angular dependence of the scattering properties. We then couple this approach to an LED light extraction model and predict how surface roughness impacts light extraction. We focus on two important cases, thin-film LEDs and volumetric LEDs. We show that optical losses in the LED dictate light extraction, and that volumetric LEDs offer an opportunity for ultimate efficiency.
55 citations
TL;DR: The proposed motion estimation algorithm improves the average peak signal-to-noise ratio and the average structural similarity of the interpolated frames by up to 5.31 dB and 0.053, respectively, compared to conventional motion estimation algorithms.
Abstract: In this paper, we propose a new motion estimation algorithm to be used for motion-compensated frame rate up-conversion. The proposed algorithm independently carries out motion estimations in both forward and backward directions, and selects a more reliable one between forward and backward motion vectors by evaluating the motion vector reliability from the viewpoint of the interpolated frame. The proposed algorithm smooths and refines both the forward and backward motion vectors before selecting the reliable one. This procedure helps to select the reasonable motion estimation direction. In identifying the motion vector outliers, the proposed algorithm uses a circular range of which center is located at the mean of the eight neighboring motion vectors of the motion vector being processed. Experimental results using 1720 test images show that the proposed motion estimation algorithm improves the average peak signal-to-noise ratio and the average structural similarity of the interpolated frames by up to 5.31 dB and 0.053, respectively, compared to conventional motion estimation algorithms.
TL;DR: In this article, a nematic display with three electrodes and double fringing fields was proposed, which exhibits submillisecond gray-to-gray response time and high contrast ratio.
Abstract: A nematic display with three electrodes and double fringing fields is proposed. Both top and bottom substrates have pixel and common electrodes to generate complementary fringing fields for achieving high transmittance. This mode exhibits submillisecond gray-to-gray response time and high contrast ratio. The effect of pixel misalignment on transmittance is discussed.
TL;DR: Using the fast and accurate histogram modification allows the proposed method to transform the intensity well for both image and video, providing a promising enhancement outcome with low computational cost.
Abstract: Contrast enhancement involves transforming the intensity of pixels from the original state to feature significant impaction on many display devices, including laptops, PDAs, monitors, mobile camera phones, and so on. This paper proposes a new method to enhance the contrast of the input image and video based on Bezier curve. In order to enhance the quality and reduce the processing time, control points of the mapping curve are automatically calculated by Bezier curve which performs in dark and bright regions separately. Using the fast and accurate histogram modification allows the proposed method to transform the intensity well for both image and video. Experimental results demonstrate the effectiveness of the proposed method in providing a promising enhancement outcome with low computational cost.
TL;DR: In this paper, the authors demonstrated that step-doping in the quantum barriers is effective in reducing the polarization induced fields and lowering the energy barrier for hole transport, and they proved experimentally that such InGaN/GaN LEDs with Si stepdoped quantum barriers indeed outperform LEDs with wholly Si-doped barriers in terms of output power and external quantum efficiency.
Abstract: InGaN/GaN light-emitting diodes (LEDs) make an important class of optoelectronic devices, increasingly used in lighting and displays. Conventional InGaN/GaN LEDs of c-orientation exhibit strong internal polarization fields and suffer from significantly reduced radiative recombination rates. A reduced polarization within the device can improve the optical matrix element, thereby enhancing the optical output power and efficiency. Here, we have demonstrated computationally that the step-doping in the quantum barriers is effective in reducing the polarization-induced fields and lowering the energy barrier for hole transport. Also, we have proven experimentally that such InGaN/GaN LEDs with Si step-doped quantum barriers indeed outperform LEDs with wholly Si-doped barriers and those without doped barriers in terms of output power and external quantum efficiency. The consistency of our numerical simulation and experimental results indicate the effects of Si step-doping in suppressing quantum-confined stark effect and enhancing the hole injection, and is promising in improving the InGaN/GaN LED performance.
TL;DR: In this article, the fabrication process and electrical characteristics of bottom-gate Indium Gallium Zinc Oxide (IGZO) thin-film transistors (TFTs) are reported in details.
Abstract: The fabrication process and electrical characteristics of bottom-gate Indium Gallium Zinc Oxide (IGZO) thin-film transistors (TFTs) are reported in details. The influence of post-annealing ambient (Oxygen or Nitrogen) is studied. It has been found that characteristics of TFTs strongly depend on annealing conditions. TFTs with Oxygen annealing exhibit standard TFT characteristics. In this case, we have obtained a mobility of 7.2 cm2/V·s, a subthreshold swing of 0.3 V/decade, high Ion/Ioff of 107 and low leakage current of the order of 10-13 at Vgs = -20 V. In the meantime, TFTs without a post-annealing or with Nitrogen annealing exhibited poor characteristics; more particularly the channel could not be depleted in the reverse mode. To understand the origins of this phenomenon, IGZO films from these devices have been analyzed by X-Ray Photoelectron Spectroscopy (XPS). Experimental results show that IGZO layers after annealing in N2 have higher concentration of oxygen vacancies. This is consistent with our electrical results since it is assumed that conduction in IGZO films is the result of oxygen vacancies.
TL;DR: The proposed gate driver has been successfully demonstrated in a 4.5-inch WVGA (480 × RGB × 800) TFT-LCD panel and passed reliability tests of the supporting foundry.
Abstract: A new gate driver has been designed and fabricated by amorphous silicon (a-Si) technology. With utilizing four clock signals in the design of gate driver on array (GOA), the pull-up transistor has ability for both output charging and discharging, and layout size of the proposed gate driver can be narrowed for bezel panel application. Moreover, lower duty cycle of clock signals can decrease static power loss to further reduce the overall power consumption of the proposed gate driver. The scan direction of the proposed gate driver can be adjusted by switching two direct control signals to present the reversal display of image. The proposed gate driver has been successfully demonstrated in a 4.5-inch WVGA (480 × RGB × 800) TFT-LCD panel and passed reliability tests of the supporting foundry.
TL;DR: In this paper, the spectral power distributions which maximize luminous efficacies of radiation (LERs) for white light of particular color rendering indices (R _{a}$ ) and color temperatures (CTs) were calculated.
Abstract: We calculate numerically the spectral power distributions (SPDs) which maximize luminous efficacies of radiation (LERs) for white light of particular color rendering indices ( $R _{a}$ 's) and color temperatures (CTs). We find that, except for the very highest color rendering indices, the spectra are spiky rather than continuous. We present a useful analytic expression for the dependences of the maximum white luminous efficacy of radiation (MWLER) on $R _{a}$ and CT and discuss these dependences. We propose that, for any white light source of a given $R _{a}$ and CT, its absolute spectral efficiency is simply the ratio of its LER to the MWLER at that same $R _{a}$ and CT. We discuss the absolute spectral efficiency, defined in this way, of various lighting technologies: incandescent, fluorescent, high-intensity discharge, and solid-state lighting. Finally, we discuss the possibility of alternative MWLERs based on alternative indices for color rendering quality.
TL;DR: A set of optimization-based backlight dimming algorithms are designed providing a perceptual optimal balance of clipping and leakage, if necessary, and show that the novel algorithms provide better quality at a given energy level or lower energy at agiven quality level.
Abstract: In this paper, we present a framework for modeling color liquid crystal displays (LCDs) having local light-emitting diode (LED) backlight with dimming capability. The proposed framework includes critical aspects like leakage, clipping, light diffusion and human perception of luminance and allows adjustable penalization of power consumption. Based on the framework, we have designed a set of optimization-based backlight dimming algorithms providing a perceptual optimal balance of clipping and leakage, if necessary. The novel algorithms are compared with several other schemes known from the literature, using both objective measures and subjective assessment. The results show that the novel algorithms provide better quality at a given energy level or lower energy at a given quality level.
TL;DR: In this article, the performance of a conformal-shaped phosphor coating fabricated using pulsed spray techniques on horizontal LED chips was investigated and the results revealed that the LED devices with multilayer phosphor configurations emitted an average of 5.6% more radiant flux than those with mixed-phosphor configurations.
Abstract: We report an investigation of the optical performance of a conformal-shaped phosphor coating fabricated using pulsed spray techniques on horizontal LED chips. Both the nitride and YAG:Ce phosphor mixed configuration and the multilayer configuration were studied. Also, 3535-packaged LED devices with the two typical phosphor configurations were prepared and analyzed. The results revealed that the LED devices with multilayer phosphor configurations emitted an average of 5.6% more radiant flux than those with mixed phosphor configurations. However, such LED devices presented an interesting reversed tendency in the luminosity measurements, which were 0.3 lm and 6 lm lower at 10 mA and 350 mA, respectively. Finally, the color rendering index (CRI) and correlated color temperature (CCT) homogeneity of the LED devices were further analyzed. A twofold reduction in CCT variation was observed compared with the conventional phosphor coating methods. It was found that the mixed phosphor LED devices demonstrated outstanding angular CCT distributions for viewing angles ranging from ${-}{\hbox{80}}^{\circ}$ to 0 $^{\circ}$ , and a CCT variation of only 45 K was detected, while the multilayer phosphor coating had higher color rendering capabilities, reaching a ${\rm CRI}_{\rm general}$ value as high as 85.6. A promising guideline found through this work is that the pulse-sprayed conformal phosphor configuration would particularly be able to improve the light quality of LED devices by a significant amount: the mixed phosphor configuration achieves excellent CCT homogeneity, and the multilayer phosphor configuration reveals a novel concept for fabricating a low-CCT and high-CRI LED device with less nitride phosphor. The findings of our research should provide valuable insight to LED industries.
TL;DR: In this article, a physically-based compact model for the sub-threshold behavior in a TFT with an amorphous semiconductor channel is presented, where both drift and diffusion current components are considered and combined using an harmonic average.
Abstract: In this paper, we present a physically-based compact model for the sub-threshold behavior in a TFT with an amorphous semiconductor channel. Both drift and diffusion current components are considered and combined using an harmonic average. Here, the diffusion component describes the exponential current behavior due to interfacial deep states, while the drift component is associated with presence of localized deep states formed by dangling bonds broken from weak bonds in the bulk and follows a power law. The proposed model yields good agreement with measured results.
TL;DR: An advanced backlight dimming technique that preserves the quality of color and details in images even when the backlight luminance of liquid crystal display (LCD) devices is lowered is proposed.
Abstract: In this paper, we propose an advanced backlight dimming technique that preserves the quality of color and details in images even when the backlight luminance of liquid crystal display (LCD) devices is lowered. The proposed backlight dimming technique consists of the following two steps: backlight luminance level selection and pixel compensation. In the first step, to reduce power consumption, the proposed approach selects an optimal level of backlight luminance for a given image based on image quality evaluation that considers the peak signal-to-noise ratio (PSNR) and color distortion level. In the second step, it adaptively adjusts the RGB ratio depending on image details, thereby enhancing image color and details, which are degraded by the lowered backlight luminance level calculated in the first step. The simulation results showed that the proposed method successfully selected the optimal backlight luminance level and prevented severe color distortion, while the benchmark method induced severe color distortion in some images. In addition, for the same backlight luminance level, pixel compensation in the proposed method reduced color difference for color distortion evaluation and the loss rate of edge strength, which showed detail loss by up to 3.58% and 40.55%, compared to benchmark methods, respectively.
TL;DR: A hybrid algorithm for 2D-to-3D conversion in 3D displays is proposed which can be reduced by 25%-35% and the depth perception score is between 75 and 85, so the human eye cannot sense the noticeable differences from the final 3D rendering.
Abstract: In recent years, 3D display technology has been receiving increasingly more attention. The most intuitive 3D method is to use two temporally synchronized video streams for the left and right eyes, respectively. However, traditional 2D video contents are captured by one camera, and in order to synthesize the left and right views as the behavior of two cameras, depth map information is required. In this paper, we propose a hybrid algorithm for 2D-to-3D conversion in 3D displays; it is a good way to solve the problem of traditional 2D video contents which need to generate 3D effects in 3D displays. We choose three depth cues for depth estimation: motion information, linear perspective, and texture characteristics. Moreover, we adopt a bilateral filter for depth map smoothing and noise removal. From the experimental results, execution time can be reduced by 25%-35% and the depth perception score is between 75 and 85. Thus, the human eye cannot sense the noticeable differences from the final 3D rendering. Furthermore, it is very suitable to apply our proposed hybrid algorithm to 2D-to-3D conversion in 3D displays.
TL;DR: The presented touch controller is designed with fast sensing methods which are proposed to enhance reporting rate and to reduce power consumption, and their implementation and experimental results are described in detail.
Abstract: In tablet touch applications, fast sensing is essential to enhance reporting rate and low power consumption is also essential to prolong battery life. To satisfy both essential demands, a fast and energy efficient single-chip touch controller for medium size (7 to 11.6 inch) of capacitive touch screen panels (TSP) is presented. The presented touch controller is designed with fast sensing methods which are proposed to enhance reporting rate and to reduce power consumption. In this paper, the proposed fast sensing methods are described in detail with their implementation and experimental results. The presented touch controller consumes power of 47.50 mA at 10.1 inch TSP, providing the minimum reporting rate of 129 Hz under 10 simultaneous touches.
TL;DR: A pixel circuit on glass using hydrogenated amorphous silicon (a-Si:H) for driving polymer-stabilized blue-phase liquid crystal displays (BPLCDs) is presented in this paper.
Abstract: We present a new pixel circuit on glass using hydrogenated amorphous silicon (a-Si:H) for driving polymer-stabilized blue-phase liquid crystal displays (BPLCDs). Different from conventional nematics, BPLC demands a large dielectric anisotropy in order to lower the operation voltage. As a result, the pixel's capacitance is increased by ~ 10t, which seriously limits the charging capability and optical efficiency. Simulation results show that the average error rate of storage voltage in pixel circuit is below 5.14% for 180 Hz operating frequency.
TL;DR: In this paper, thermal oxidation of metallic copper (Cu) at different temperatures was used to obtain p-type thin-film transistors with On/Off ratios of 2.2, 1.9 and 1.6.
Abstract: Thin-films of copper oxide $({\hbox{Cu}}_{x}{\hbox{O}})$ were produced by thermal oxidation of metallic copper (Cu) at different temperatures (150–450 $\ ^{\circ}{\hbox{C}}$ ). The films produced at temperatures of 200, 250 and 300 $\ ^{\circ}{\hbox{C}}$ showed high Hall motilities of 2.2, 1.9 and 1.6 ${\hbox{cm}}^{2}\ {\hbox{V}}^{-1}{\hbox{s}}^{-1}$ , respectively. Single ${\hbox{Cu}}_{2}{\hbox{O}}$ phases were obtained at 200 $\ ^{\circ}{\hbox{C}}$ and its conversion to CuO starts at 250 $\ ^{\circ}{\hbox{C}}$ . For lower thicknesses $\sim$ 40 nm, the films oxidized at 250 $\ ^{\circ}{\hbox{C}}$ showed a complete conversion to CuO phase. Successful thin-film transistors (TFTs) were produce by thermal oxidation of a 20 nm Cu film, obtaining p-type ${\hbox{Cu}}_{2}{\hbox{O}}$ (at 200 $\ ^{\circ}{\hbox{C}}$ ) and CuO (at 250 $\ ^{\circ}{\hbox{C}}$ ) with On/Off ratios of ${\hbox{6}}\times {\hbox{10}}^{1}$ and ${\hbox{1}}\times {\hbox{10}}^{2}$ , respectively.
TL;DR: In this paper, a time-multiplexed dual-view display device using a blue phase liquid crystal is proposed to achieve high transmittance and fast response, which can present two different images to viewers sequentially.
Abstract: A time-multiplexed dual-view display device using a blue phase liquid crystal is proposed. In this design, a vertical field switching blue phase liquid crystal display (VFS-BPLCD) panel is used to achieve high transmittance and fast response. Combined with a directional backlight module, this device can present two different images to viewers sequentially. The proposed device has advantage in full spatial resolution.
TL;DR: In this article, a gate driver integrated with hydrogenated amorphous-silicon thin-film transistors (a-Si:H TFTs) for active-matrix flat-panel display (AM-FPD) is carried out.
Abstract: A thorough study on the gate driver integrated with hydrogenated amorphous-silicon thin-film transistors (a-Si:H TFTs) for active-matrix flat-panel display (AM-FPD) is carried out in this work. The single stage circuit of the a-Si:H gate driver consists of input, pull-up, pull-down, and low-level holding units. The operation principle of the driver is described in detail. The subtle static and dynamic characteristics of the a-Si:H TFT based circuit are analyzed systematically for the first time. The long term reliability issue is also addressed. Design equations for determining the device sizes of the circuit are derived. The TFT-LCD panels integrated with the designed gate driver are fabricated to verify the design efficiency.
TL;DR: In this article, the authors report a dependence of the electrical stability of amorphous indium-gallium-zincoxide (a-IGZO) thin-film transistors (TFTs).
Abstract: We report channel length L ( L ranging from 2 to 40 μm) dependence of the electrical stability of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs). The a-IGZO TFTs employ a coplanar structure with a SiNx interlayer used to dope the source/drain regions. After application of positive gate bias stress (PBS), short-channel devices ( L = 2 μm) exhibit smaller threshold voltage shifts ( ΔVth) compared to longer-channel devices ( L ≥ 4 μm). It is proposed that carrier diffusion takes place from the high carrier concentration regions under the SiN∞ interlayer to the intrinsic channel region, thereby shifting the Fermi level closer to the conduction band. Higher Fermi levels mean less defect states available for carrier trapping - hence the small ΔVth in short devices under PBS.
TL;DR: Based on the algorithm, a 42-in backlight module with white light-emitting diode (LED) devices was driven by a local dimming control core, and the block-wise register approach substantially reduced the number of required line-buffers and shortened the latency time.
Abstract: The local-dimming backlight has recently been presented for use in LCD TVs. However, the image resolution is low, particularly at weak edges. In this work, a local-dimming backlight is developed to improve the image contrast and reduce power dissipation. The algorithm enhances low-level edge information to improve the perceived image resolution. Based on the algorithm, a 42-in backlight module with white light-emitting diode (LED) devices was driven by a local dimming control core. The block-wise register approach substantially reduced the number of required line-buffers and shortened the latency time. The measurements made in the laboratory indicate that the backlight system reduces power dissipation by an average of 48% and exhibits no visible distortion compared relative to the fixed backlighting system. The system was successfully demonstrated in a 42-in LCD TV, and the contrast ratio was greatly improved by a factor of 100.
TL;DR: In this article, a figure of merit (FoM) defined as the ratio of Kerr constant to response time is used to characterize and compare the electro-optic performance of polymer-stabilized blue phase liquid crystals (BPLCs).
Abstract: A figure of merit (FoM), defined as the ratio of Kerr constant to response time, is used to characterize and compare the electro-optic performance of polymer-stabilized blue phase liquid crystals (BPLCs). Increasing the dielectric anisotropy of LC host enhances Kerr constant and lowers the operation voltage, but its associated high viscosity dramatically increases the response time. As a result, the FoM may not be necessarily higher. For a given BPLC device, an optimal temperature exists where FoM reaches maximum. The proposed FoM provides useful guidelines for optimizing BPLCs for display and photonic applications.