Kunio Masumo

A full-color LCD addressed by poly-Si TFTs fabricated below 450 degrees C

Poly-Si thin-film transistors (TFTs) fabricated with a maximum processing temperature of 450 degrees C by means of laser-induced crystallization of a-Si are discussed. These devices show high mobilities (50 cm/sup 2//V-s), low threshold voltages (2 V), low off current (10/sup -12/ A), and high reliability. A 3.5-in.-diagonal full-color liquid-crystal display addressed by these poly-Si TFTs is presented. >

Fabrication of A-Si:H Solar cells on high haze SnO 2 :F thin films

In this work we report on the properties of amorphous silicon (a-Si:H) p-i-n solar cells fabricated on glass substrates covered with extremely high haze fluorinedoped tin oxide (SnO2:F) transparent conductive oxide (TCO) thin films, HU-TCO. The HU-TCO shows high haze value thorough the whole optical region where a-Si:H and microcrystalline silicon (μc-Si:H) solar cells are sensitive. We demonstrate here that open-circuit voltage (Voc) and fill factor (FF) of a-Si:H solar cells fabricated on HU-TCOs does not decrease significantly compared to the cells on conventional pyramidal texture TCOs. We also demonstrate here that Voc and FF of a-Si:H solar cells depend on not only surface morphology of TCOs, but also strongly depend on thickness and deposition conditions of the solar cells.

Low Temperature Polysilicon TFTs by Non-Mass-Separated Ion Flux Doping Technique

A low temperature and hi8h throughput self aligned poly-Si TFT fabrication process has been developed. The process includes two key techniques. The first one is a laser induced crystallization of a-Si, occurring in the solid phase, using a high beam scanning speed. The second is a large diameter ion flux doping without nass separation. The maximum processing temperature is 450t, which is sufficiently low to use inexpensive glass substrates. With this process, exeellent poly-Si TFT characieristics of Ion/Ioff>106 and 4 ru=40em2/ys were obtained.

Effect of a zirconium oxide undercoat on microstructure and properties of tin-doped indium oxide films for organic light emitting devices

Abstract ITO films deposited on ZrO 2 undercoats by sputtering were investigated. The ITO films have a fine grain structure, compared to a grain–subgrain structure of conventional ITO films grown on a glass substrate. The grain structure of the ITO films grown on ZrO 2 consists of 30–50 nm wide almost parallel-sided columns. The surface grains have a good uniformity in shape and size. The microstructure and electrical properties of the ITO films changed with increasing ZrO 2 thickness. This indicates that the microstructure and properties of ITO films can be controlled by the ZrO 2 film thickness. The OLED fabricated on the ITO films on ZrO 2 worked with lower driving voltage than the one fabricated on conventional ITO films at the same luminance.

Low temperature fabrication of poly-Si TFT by laser induced crystallization of a-Si

Abstract Poly-Si TFTs were fabricated by means of laser-induced crystallization of PECVD a-Si in which the maximum process temperature was 450°C. These devices showed high field effect mobilities (50cm2/Vs), low off current (10–12A), and high reliability. A 3.5-in diagonal full-color LCD addressed by these poly-Si TFTs was fabricated and produced beautiful video images.

A full colour LCD addressed by poly Si TFTS fabricated at low temperature below 450 degrees C

A process below 450 degrees C has been developed for poly-Si thin-film transistor (TFTs). The devices have higher mobility ( approximately 50 cm/sup 2//V-s) and higher reliability than a-Si TFTs. A 3.5-in. full-colour liquid-crystal display addressed by these poly-Si TFTs is described.<<ETX>>

Low-Temperature Polysilicon Thin Film Transistors by Non-Mass-Separated Ion Flux Doping Technique

A low-temperature, high-throughput self-aligned poly-Si TFT fabrication process has been developed. The process includes two key techniques. The first one is a laser-induced crystallization of a-Si occurring in the solid phase using a CW Ar+ laser beam with high scanning speed, which was previously reported. The second is large-diameter ion flux doping without mass separation. The maximum processing temperature is 450°C, which is sufficiently low for use of inexpensive glass substrates. With this process, excellent poly-Si TFT characteristics of Ion/Ioff>106 and µFE=40 cm2/(V s) were obtained.

Improved light-trapping effect in a-Si:H / μC-Si:H tandem solar cells by using high haze SnO 2 :F thin films

In this paper we report on the fabrication of amorphous silicon (a-Si:H) / microcrystalline silicon (μc- Si:H) p-i-n tandem solar cells on high haze fluorine-doped tin oxide (SnO2:F) transparent conductive oxide (TCO) thin films, type-HU. The HU-TCO has double texture morphology on its surface and shows high haze value through the whole optical region where the tandem solar cells are sensitive. We demonstrate here that light-trapping effect is improved by using HU-TCO. HU-TCO provided higher short-circuit current than conventional pyramidal TCO when i-layer thicknesses of a-Si:H and μc- Si:H of tandem solar cell were 0.35 and 1.5 µm, respectively. Quantum efficiency of bottom μc-Si:H cell was improved by 1 mA/cm2 by using HU-TCO.

Low-leakage current polysilicon TFTs for LCD pixel addressing

The leakage current characteristics of low-temperature polysilicon TFTs (thin-film transistors) below 450 degrees C have been investigated. It was confirmed that the laser-induced crystallized polysilicon with temperature below 450 degrees C has good physical properties and device characteristics in TFT, equal to those of polysilicon with a process temperature of around 600 degrees C. Reduction of leakage current at higher signal voltage could be achieved by the optimization of the geometrical structure with the laser-induced crystallized polysilicon TFT. The low leakage current characteristics at the higher signal voltage may enlarge the applicable field in the higher-performance display. For example, these improved characteristics make it possible to apply higher voltage for addressing pixels of normally white TN and LC (liquid crystal) polymer composite mode.<<ETX>>

Relation of TCO surface texture shape to a-Si/μc-Si tandem cell performance on W-texture SnO 2 :F TCO substrates

Double-texture (W-texture) TCO, which was named “HU-TCO”, has a combination of 300–500nm height and over 1μm width hills which are covered with submicron-size pyramidal texture that leads to high haze value in a wide wavelength range. We studied the relation between the bottom current of the a-Si:H/μc-Si:H tandem solar cells and the TCO texture indexes, such as the haze ratio at 800nm, and light scattering angle distribution. There is a positive correlation between bottom current and haze ratio at 800nm; however it was observed that the bottom current hit a peak at very high haze value. We modified amorphous p-layer of top cell and confirmed that the player configuration strongly affected Voc. Appropriate player configuration not only affected the Voc but also further increased the bottom current on the HU-TCO with high hills.