Design of a Multifunctional Double-Active-Layer Thin-Film Transistor for Photosensing Applications

Photocurrent generation from infrared and thin-film transistor (TFT) driving properties were simultaneously achieved with a hydrogenated amorphous silicon/a-SiGe:H double-active-layer structure. The proposed double layer showed electrical performance degradation due to the large series resistance from the thick active structure. By reducing the thickness of a-SiGe:H only in the driving TFT, a compatible field-effect mobility of 0.29 cm
²
/V·s was achieved, which can fully drive the TFT. In the photosensor TFT, a higher photosensitivity was obtained with a thick a-SiGe:H layer. This implies that the multifunctional double active layer and new process effectively realized the two different properties at the same time.