Jun-ho Song

3.2: Integrated a‐Si Gate Driver Circuit for TFT‐LCD Panel

We developed an a-Si TFT-LCD panel with integrated gate driver circuit using a standard 5-MASK process. To minimize the effect of the a-Si TFT current and LCs capacitance variation with temperature, we developed a new a-Si TFT circuit structure and minimized coupling capacitance by changing vertical architecture above gate driver circuit. Integration of gate driver circuit on glass substrate enables single chip and 3-side free panel structure in a-Si TFT-LCD of QVGA(240*320) resolution.

A highly sensitive and low‐noise IR photosensor based on a‐SiGe as a sensing and noise filter: Toward large‐sized touch‐screen LCD panels

— The a-SiGe TFT photosensor for embedded touch-screen panels (TSPs) was characterized by comparison with an a-Si sensor. The photoresponse of an a-SiGe sensor at a 850-nm wavelength was much higher than that of a-Si, indicating that a-SiGe is a strong candidate material for an IR sensor. In order to increase the signal-to-noise ratio, the incident visible light was filtered by incorporating a bandpass-filter layer. An a-SiGe IR-sensor-embedded LCD panel was successfully demonstrated, showing an excellent multitouch property independent of ambient-light conditions. This technology can be widely used in multifunctional TSPs.

Characteristics of a-SiGe:H Thin Film Transistor Infrared Photosensor for Touch Sensing Displays

Photo-generation properties in an amorphous SiGe:H thin film transistor (TFT) were characterized by analyzing the electrical performances under illumination. The a-SiGe:H TFT showed a higher photo sensitivity at the wavelength of IR regime, and as a-SiGe:H layer was thicker, the generated photo currents proportionally increased due to the higher photon absorption. The increase of Ge composition led to the reduction of optical energy band gap. However, the photo sensitivity was not increased with lowering of energy band gap due to the creation of defects in the layer. The photo generation was dependent on the geometry of TFT, such as channel width and length. In particular, it was observed that regions under the source/drain electrode played a critical role in generating the photo currents which was demonstrated by technology computer-aided design simulation. Based on these, the generation of photo current and the photo field effect in a-SiGe:H TFT were interpreted using band diagrams. A-SiGe:H IR photosensor-embedded liquid crystal display panel was successfully demonstrated, indicating that these can be useful to broad use in the photo-type touch sensor, photo detector, and solar cell devices.

P-218L: Late-News Poster: A Compact and Cost-Efficient TFT-LCD through the Triple-Gate Pixel Structure

To realize a compact and cost-efficient TFT-LCD for PMP or CNS applications, we propose a 4.0″ WqVGA(480×272) a-Si TFT-LCD through the triple-gate pixel structure. By using the triple-gate pixel structure 1-chip TFT-LCD is available for CNS applications. and this 1-chip TFT-LCD cuts costs by fifteen percent, or more. A double Amorphous Silicon Gate(ASG) solves secondary problems such as short gate line time and small layout area which are caused by the triple-gate pixel structure.

ASG(amorphous silicon TFT gate driver circuit) technology for mobile TFT‐LCD panel

Abstract We developed an a‐Si TFT‐LCD panel with integrated gate driver circuit using a standard 5‐MASK process. To minimize the effect of the a‐Si TFT current and LCs capacitance variation with temperature, we developed a new a‐Si TFT circuit structure and minimized coupling capacitance by changing vertical architecture above gate driver circuit. Integration of gate driver circuit on glass substrate enables single chip and 3‐side free panel structure in a‐Si TFT‐LCD of QVGA (240 × 320) resolution. And using double ASG structure the dead space of TFT‐LCD panel could be further decreased.

Photo-Related Stress Effects in a-SiGe:H Thin Film Transistors for Infrared Image Sensors

The effects of photo-related stress on the electrical performances of a-SiGe:H thin-film transistors (TFTs) were investigated in comparison with a-Si:H TFTs. Compared with a-Si:H TFTs, the a-SiGe:H TFTs show better stability to the light stress because the number of electrons involved in the creation of dangling bonds are smaller in a-SiGe:H TFTs, resulting in less light-induced degradation. However, a larger threshold voltage shift from the positive gate bias was observed due to the higher number of weak bonds in a-SiGe:H TFTs, which leads to a higher gate bias instability than is observed for a-Si:H TFTs. The temperature dependences of the electrical properties in a-SiGe:H TFTs were observed, and they indicated that a-SiGe:H TFTs follow a thermally activated behavior pattern. Based on the thermally activated behavior, a new model predicting the lifetime of a-SiGe:H TFT image sensors was proposed. The instability of the drain current with respect to the stress time under an electrical bias and light was estimated. Based on the calculated lifetime, the a-SiGe:H TFTs are predicted to be reliable for long-term applications in image sensors.

New RGB primary for various multimedia systems

Color gamut is one of the most important performance indicators of multimedia systems because a wide color gamut enables the reproduction of more real surface colors. The color gamut of multimedia systems depends on the RGB (red-green-blue) primary. There are various RGB primaries, such as ITU-R BT.709, ITU-R BT.2020, sRGB, Adobe RGB, and DCI-P3. ITU-R BT.709 and sRGB have a very small color gamut, while ITU-R BT.2020 has an extremely wide one. Adobe RGB and DCI-P3 have RGB primaries with the characteristics of color printers and digital cinema projectors, respectively. Also, some of these RGB primaries are not compatible with each other. Thus, the contents of a system should be converted for use in other systems. This paper proposes an RGB primary for use in various multimedia systems. In the proposed method, sRGB, Adobe RGB, and DCI-P3 – the most frequently used RGB primaries – are unified. In this paper, the color gamut efficiency and human visual preference of the proposed RGB primary are checked. The proposed RGB primary is expected to be utilized as an international-standard RGB primary for multimedia systems.

33.3: A 14.1‐Inch WXGA+ LCD Panel Using Hybrid Silicon Thin Film Transistors

A hybrid silicon technology (HyST) thin film transistor (TFT) process using a diode-pumped solid state (DPSS) laser has been developed by implementing low-temperature poly-Si (LTPS) TFTs with a-Si:H TFTs on the same substrate. HyST TFTs are deployed on the peripheral area of a panel for integrated gate driver circuits and a-Si:H TFTs are used as switching devices for pixels in the active display area. This technology is based on the current a-Si:H TFT fabrication processes without additional ion-doping and activation processes. Field effect mobilities of 4 ∼ 5 cm2/V⋅s and 0.5 cm2/V⋅s for HyST and a-Si:H TFTs, respectively, are obtained. Low power consumption, high speed, small integration area, high reliability, and low photosensitivity are achieved by means of HyST TFTs, compared to gate driving circuits integrated with a-Si:H TFTs. A 14.1-inch WXGA+ (1440×900) LCD panel has been demonstrated using the new HyST TFT process.

The Study of Sputtered SiGe Thin Film Growth for Photo-detector Application

Samsung Display LCD RD Revised May 3, 2012; Accepted May 10, 2012) Abstract: For the application of photo-detector as active layer, we have studied how to deposit SiGe thin film using an independent Si target and Ge target, respectively. Both targets were synthesized by purity of 99.999%. Plasma generators were generated by radio frequency (rf, 13.56 MHz) and direct current (dc) power. When Ge and Si targets were sputtered by dc and rf power, respectively, we could observe the growth of highly crystalline Ge thin film at the temperature of 400℃ from the result of raman spectroscopy and X-ray diffraction method. However, SiGe thin film did not deposit above method. Inversely, we changed target position like that Ge and Si targets were sputtered by rf and dc power, respectively. Although Ge crystalline growth without Si target sputtering deteriorated considerably, the growth of SiGe thin film was observed with increase of Si dc power. SiGe thin film was evaluated as microcrystalline phase which included (111) and (220) plane by X-ray diffraction method.Keywords: Microcrystalline SiGe, Sputtering, Raman spectroscopy, IR detector, Touch screen