Visible–near-infrared wavelength-selective imaging devices based on floating-gate phototransistors

Multispectral photodetectors are emerging devices capable of detecting photons in multiple wavelength ranges, such as the visible (VIS) and near infrared (NIR) regions. Image data acquired with these photodetectors can be used for effective object identification and navigation owing to additional information beyond human vision, including thermal images and night vision. However, this approach inevitably brings about problems of complex structures and low integration. In addition, few broad-spectrum detectors can achieve imaging in the visible and infrared bands separately, which is highly important for scene recognition and other tasks. Here, we propose a wide-spectrum photodetector integrated with a spectral separation function based on a visible light absorber/floating gate storage layer/near-infrared (NIR) photogating layer configuration. This device exhibits a negative photoresponse under infrared irradiation through the absorption of infrared light by the Ge substrate and the photogating effect and achieves a visible positive photoresponse through the absorption of visible light by MoS₂. Furthermore, based on the memory function of the device under floating gate tunneling and the bidirectional photoresponse characteristics of the device, wide-spectrum light detection and single-wavelength signal extraction are realized. Through clever changes in the gate voltage pulse, the photoresponse state of the output voltage is effectively adjusted to achieve three imaging states: visible light response only, response to both visible and infrared light, and infrared light response only. Reconfigurable wavelength-selective imaging can be achieved using different V_pgm (programming voltage) values. The proposed reconfigurable visible–infrared wavelength-selective imaging photodetector can effectively extract image information and improve the image recognition rate while ensuring a simple structure. The single-chip-based spectral separation imaging solution lays a good foundation for further development of visible–infrared vision applications.