MoS2/HfO2/Silicon-On-Insulator Dual-Photogating Transistor with Ambipolar Photoresponsivity for High-Resolution Light Wavelength Detection

Photogating detectors based on 2D materials attract significant research interests. However, most of these photodetectors are only sensitive to the incident intensities and lack the ability to distinguish different wavelengths. Color imaging based on these detectors usually requires additional optical filter arrays to collect red, green, and blue (RGB) colors in different photodetectors to restore the true color of one pixel. In this study, an MoS2/HfO2/silicon-on-insulator field effect phototransistor with wavelength distinguishing ability is presented, where the photogating effect can be simultaneously formed in the top MoS2 gate and bottom Si substrate gate. These two individual photogating effects can reduce and increase the read current in the middle 12 nm Si channel, respectively. Thus, by tuning the applied voltages on these two gates, the device can be used to obtain tunable ambipolar photoresponsivity from +7000 A W-1 (Si bottom gate dominated) to 0 A W-1 (balanced), and finally to -8000 A W-1 (MoS2 gate dominated). In addition, the experimental results show that the corresponding top gate voltage to the zero responsivity (0 A W-1) point can be positively shifted by the increasing of incident wavelength with high resolution up to 2 nm and is insensitive to the incident intensity.