We report the effects of monochromatic illumination on the electrical performance of a-SiGe:H thin-film transistor (TFT) and the use of this device as infrared (IR) image-sensing touch displays. In order to reduce the inevitable incidence of visible light into device, the visible cutting layer was designed, which played a critical role in reducing the optical noise from visible light. When the photo response was observed in real liquid crystal display (LCD) operation environment, it showed the display contents dependence, meaning that the supply of external IR light source for the touch sensing would be effective independent of any ambient light condition. Additionally, the optical noise from the display operation was eliminated using the block operation as well as the backlight IR light-emitting diode (LED) light modulation. From these, the clear touch images were successfully obtained in the a-SiGe:H photosensor embedded LCD panel.Index Terms-Amorphous SiGe, infrared (IR) detector, photosensor, thin-film transistor (TFT).

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Resistance of metal depends on temperature. Therefore, the metal can be used as a temperature sensor with a reference resistor. The reference resistor is connected serially and the voltages of the sensor metal are measured after applying DC voltage. However, it is not easy to keep the reference resistance constant while measuring temperatures. We studied the temperature dependence of resistance of oxide material to apply it to the bridge type temperature sensor which is insensitive to the environmental temperature. We made bridge type temperature sensor with oxide material and metal. The novel temperature sensor does not need a reference resistor, and composed of oxide and metal. Therefore, we could remove error induced by environmental temperature variation. Moreover, the novel bridge type temperature sensor provides higher sensitivity than conventional sensor structure. By different thermal coefficient of the oxide material, it was possible to remove an external reference resistance. The proposed bridge type temperature sensor is a self-reference temperature sensor which is insensitive to the environmental temperature.