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.