Research on color matching of LED backlight for large-color-gamut LCD application - art. no. 68410Y

Comparing with the conventional CCFL (Cold Cathode Fluorescent Lamp) backlight, three-basic-color LEDs backlight has some advantages such as good color reproduction, long life and lead free etc. Theoretically, the color gamut is determined by x, y coordinates of the three basic colors in CIE chromaticity diagram, and the x, y coordinates of each basic color can derived from the relative spectrum distribution (RSD) of the LED. In this paper, the red, green and blue LEDs' RSD models are established to calculate and analyze the color gamut of a backlight. By simulating those models, the relationships that the color gamut of a LED backlight varies with each color are analyzed, and the optimum combination of three colors is obtained within the given wavelengths ranges. Moreover, the combinations of three colors for the gamut of 115% NTSC and 110% NTSC are plotted in pictures, respectively.

High Quality AlGaN Grown on GaN Template with HT-AlN Interlayer

When AlGaN is grown on GaN template, crack networks invariably generate when the thickness of the AlGaN layers over GaN exceeds the critical value. We used thin high temperature deposited AlN layer (HT-AlN) as the interlayer between GaN template and AlGaN epilayer which was very effective in eliminating the cracks in AlGaN epilayer. AlGaN layers with high Al mole fractions were also grown. Characterization showed that the crystalline quality of AlGaN epilayer was fairly good even when the At mole fraction was high.

A power-saving scheme for IEEE 802.11 Ad hoc networks

In the Wireless Local Area Networks (WLANs), the terminals are often powered by battery, so the power-saving performance of the wireless network card is a very important issue. For IEEE 802.11 Ad hoc networks, a power-saving scheme is presented in Medium Access Control (MAC) layer to reduce the power consumption by allowing the nodes enter into the sleep mode, but the scheme is based on Time-Drive Scheme (TDS) whose power-saving efficiency becomes lower and lower with the network load increasing. This paper presented a novel energy-saving mechanism, called as Hybrid-Drive Scheme (HDS), which introduces into a Message.-Drive Scheme (MDS) and combines MDS with the conventional TDS. The MDS, could obtain high efficiency when the load is heavy; meanwhile the TDS has high efficiency when the network load is small. The analysis shows that the proposed HDS could obtain high energy-efficiency whether the network load is light or heavy and have higher energy-saving efficiency than conventional scheme in the IEEE 802.11 standard.

The status, limits and countermeasures in the development of the silicon microelectronics industry

In this paper.. the status and limits in the development of the silicon microelectronics industry are presented briefly. The key countermeasures given are use of the new structure materials and the new device structures.

A silicon capacitive microphone based on oxidized porous silicon sacrificial technology

In this paper, a new capacitive microphone fabrication technology is proposed. It describes using the oxidized porous silicon sacrificial technology to make air gap and using KOH etching technique to make the backplate containing acoustic holes based on the principle that the heavy p(+)-doping silicon can be nearly etched in KOH solution. The innovation of the method is using oxidized porous silicon technology. The sensitivity of the fabricated microphone is from -55dB ( 1.78mV/Pa) to -45dB (5.6mV/Pa) in the frequency range of 500Hz to 25kHz. Its cut-off frequency is higher than 20kHz.

Magnetic Properties of FePt Nanoparticles Prepared by a Micellar Method

FePt nanoparticles with average size of 9 nm were synthesized using a diblock polymer micellar method combined with plasma treatment. To prevent from oxidation under ambient conditions, immediately after plasma treatment, the FePt nanoparticle arrays were in situ transferred into the film-growth chamber where they were covered by an SiO2 overlayer. A nearly complete transformation of L1(0) FePt was achieved for samples annealed at temperatures above 700 A degrees C. The well control on the FePt stoichiometry and avoidance from surface oxidation largely enhanced the coercivity, and a value as high as 10 kOe was obtained in this study. An evaluation of magnetic interactions was made using the so-called isothermal remanence (IRM) and dc-demagnetization (DCD) remanence curves and Kelly-Henkel plots (Delta M measurement). The Delta M measurement reveals that the resultant FePt nanoparticles exhibit a rather weak interparticle dipolar coupling, and the absence of interparticle exchange interaction suggests no significant particle agglomeration occurred during the post-annealing. Additionally, a slight parallel magnetic anisotropy was also observed. The results indicate the micellar method has a high potential in preparing FePt nanoparticle arrays used for ultrahigh density recording media.

Effects of annealing treatment on the formation of CO2 in ZnO thin films grown by metal-organic chemical vapor deposition

Post-growth annealing was carried out on ZnO thin films grown by metal-organic chemical vapor deposition (MOCVD). The grain size of ZnO thin film increases monotonically with annealing temperature. The ZnO thin films were preferential to c-axis oriented after annealing as confirmed by Xray diffraction (XRD) measurements. Fourier transformation infrared transmission measurements showed that ZnO films grown at low temperature contains CO2 molecules after post-growth annealing. A two-step reaction process has been proposed to explain the formation mechanism of CO2, which indicates the possible chemical reaction processes during the metal-organic chemical vapor deposition of ZnO films.

A study of indium incorporation in In-rich InGaN grown by MOVPE

InGaN/GaN heterostructures have been deposited onto (0 0 0 1) sapphire by our home-made low pressure MOVPE with different growth parameters. It has been noted that the indium incorporation depends by a complex way on a number of factors. In this work, the effect of substrate temperature, trimethylindium input flow and V/III ratio on the indium incorporation has been investigated. Finally, by optimizing the growth parameters, we made a series of single-phase InGaN samples with indium content from 10% up to 45%.

Strain-Compensated InGaAs/InAlAs Quantum Cascade Detector of 4.5 mu m Operating at Room Temperature

We present a strain-compensated InP-based InGaAs/InAlAs photovoltaic quantum cascade detector grown by solid source molecular beam epitaxy. The detector is based on a vertical intersubband transition and electron transfer on a cascade of quantum levels which is designed to provide longitudinal optical phonon extraction stairs. By careful structure design and growth, the whole epilayer has a residual strain toward InP substrate of only -2.8 x 10(-4). A clear narrow band detection spectrum centered at 4.5 mu m has been observed above room temperature for a device with 200 x 200 mu m(2) square mesa.

Photoluminescence spectroscopy and positron annihilation spectroscopy probe of alloying and annealing effects in nonpolar m-plane ZnMgO thin films

Temperature-dependent photoluminescence characteristics of non-polar m-plane ZnO and ZnMgO alloy films grown by metal organic chemical vapor deposition have been studied. The enhancement in emission intensity caused by localized excitons in m-plane ZnMgO alloy films was directly observed and it can be further improved after annealing in nitrogen. The concentration of Zn vacancies in the films was increased by alloying with Mg, which was detected by positron annihilation spectroscopy. This result is very important to directly explain why undoped Zn1-xMgxO thin films can show p-type conduction by controlling Mg content, as discussed by Li [Appl. Phys. Lett. 91, 232115 (2007)].

Influence of band bending and polarization on the valence band offset measured by x-ray photoelectron spectroscopy

The influence of band bending and polarization on the valence band offset measured by x-ray photoelectron spectroscopy (XPS) is discussed, and a modification method based on a modified self-consistent calculation is proposed to eliminate the influence and thus increasing the precision of XPS. Considering the spontaneous polarization at the surfaces and interfaces and the different positions of Fermi levels at the surfaces, we compare the energy band structures of Al/Ga-polar AlN/GaN and N-polar GaN/AlN heterojunctions, and give corrections to the XPS-measured valence band offsets. Other AlN/GaN heterojunctions and the piezoelectric polarization are also introduced and discussed in this paper.

Measurement of GaN/Ge(001) Heterojunction Valence Band Offset by X-Ray Photoelectron Spectroscopy

X-ray photoelectron spectroscopy has been used to measure the valence band offset (VBO) at the GaN/Ge heterostructure interface. The VBO is directly determined to be 1.13 +/- 0.19 eV, according to the relationship between the conduction band offset Delta E-C and the valence band offset Delta E-V : Delta E-C = E-g(GaN) - E-g(Ge) - Delta E-V, and taking the room-temperature band-gaps as 3.4 and 0.67 eV for GaN and Ge, respectively. The conduction band offset is deduced to be 1.6 +/- 0.19 eV, which indicates a type-I band alignment for GaN/Ge. Accurate determination of the valence and conduction band offsets is important for the use of GaN/Ge based devices.

Valence band offset of MgO/TiO2 (rutile) heterojunction measured by X-ray photoelectron spectroscopy

The valence band offset (VBO) of MgO/TiO2 (rutile) heterojunction has been directly measured by Xray photoelectron spectroscopy. The VBO of the heterojunction is determined to be 1.6 +/- 0.3 eV and the conduction band offset (CBO) is deduced to be 3.2 +/- 0.3 eV, indicating that the heterojunction exhibits a type-I band alignment. These large values are sufficient for MgO to act as tunneling barriers in TiO2 based devices. The accurate determination of the valence and conduction band offsets is important for use of MgO as a buffer layer in TiO2 based field-effect transistors and dye-sensitized solar cells.

Measurement of w-InN/h-BN Heterojunction Band Offsets by X-Ray Photoemission Spectroscopy

X-ray photoelectron spectroscopy has been used to measure the valence band offset (VBO) of the w-InN/h-BN heterojunction. We find that it is a type-II heterojunction with the VBO being -0.30 +/- A 0.09 eV and the corresponding conduction band offset (CBO) being 4.99 +/- A 0.09 eV. The accurate determination of VBO and CBO is important for designing the w-InN/h-BN-based electronic devices.

Optical properties of Mn+ doped GaAs

The above work was supported by the national Basic Research Program of China (2006cb604904, 2006cb604908), the hi-tech R & D program of China (2006aa03z0408, 2006aa03z0404), the scientific research Fund of Central South University of Forstry and Technology.