Photoresponsivity Enhancement and Extension of the Detection Spectrum for Amorphous Oxide Semiconductor Based Sensors

In this study, indium gallium zinc oxide (InGaZnO [IGZO]) active layer capped with an ultrathin p‐type stannous oxide (SnO) is demonstrated to be a thin film transistor (TFT) for color scanning and photosensing device applications. Typically, the sole IGZO‐based TFT is blind to visible light and hard to be developed for visible light sensing. The combination of IGZO and SnO layers can extend the light detection spectrum into visible light wavelengths and ameliorate the photosensing characteristics. The optical responsivity and signal to noise ratio can even be enhanced from 1.05 × 10−2 to 398.02 A W−1 and from 2.1 × 101 to 6.8 × 105 with at least four orders of magnitude, respectively. With the detailed material analysis and physical model discussed, it suggests that the large amount of additional light‐excited carrier generated in the capping layer is the key factor for the significant improvement. Furthermore, the phenomenon of persistent photoconductivity can be effectively suppressed by its natural recombination under the heterojunction structure without applying charge‐pumping method. The electrical uniformity of the sensor device is also highly potential for the next‐generation displays integrating the photosensing functions. An ultrathin p‐type stannous oxide with suitable bandgap, high stability, good process compatibility, and uniformity is proposed to be the light‐absorbing layer, that improves the optical responsivity and signal to noise ratio of an amorphous indium gallium zinc oxide based sensor thin film transistor by at least four orders of magnitude. Besides, the persistent photoconductivity effect can also be suppressed by its heterojunction structure.