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Abstract— 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.

The a-SiGe:H TFT photosensor for embedded touch screen panel (TSP) was characterized compared with a-Si:H TFT. The photo sensitivity of a-SiGe:H sensor at 850 nm IR light was ~15 times higher than that of a-Si:H, indicating that a-SiGe:H is a strong candidate material to an IR sensor. In order to increase the signal to noise ratio, the incoming of visible layer was blocked by visible cutting layer. A 40-inch panel in which a-SiGe:H IR sensor was embedded was successfully demonstrated, showing the excellent multi-touch property without ambient light interferences. This technology can be applied to broad use in the multi-functional TSPs without ambient light limitation.

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