Image sensors with an in-sensor computing architecture have shown great potential in meeting the energy-efficient requirements of emergent data-intensive applications, where images are processed within the photodiode arrays. It demands the composed photodiodes are reconfigurable, which are usually achieved by ambipolar two-dimensional (2D) semiconductors. To improve the ambipolar charges injection, here we report a top-gated field-effect transistor (FET) design that is of bottom van der Waals contact via transferring ambipolar 2D WSe₂ onto Pd/Cr source/drain electrodes. The devices exhibit nearly negligible effective barrier heights for both holes and electrons based on thermionic emission mode, and show an almost balanced on/off ratio in the p-branch and n-branch. By replacing the top gate with two aligned semi-gates, the devices can effectively function as reconfigurable photodiodes. They can be switched between PIN and NIP configurations via controlling the two semi-gates, exhibiting good linearity in terms of short-circuit current (I_SC) and incident light power density. The photodiode arrays are also demonstrated for in-sensor optoelectronic convolutional image processing, showing significant potential for in-sensor computing image processors.

The unique features of ambipolar two-dimensional materials open up a great opportunity to build gate-programmable devices for reconfigurable circuit applications, e.g., PN junctions for rectifier circuits. However, current-reported rectifier circuits usually consist of one gate-programmable PN junction as the rectifier and one resistor as the load, which are not conductive to voltage output and large-scale integration. Here we propose an approach of complementary gate-programmable PN junctions to assemble reconfigurable rectifier circuit, which include two symmetric back-to-back black phosphorus (BP)/hexagonal boron nitride (h-BN)/graphene heterostructured semi-gate field-effect transistors (FETs) and perform complementary NP and PN junction like complementary metal-oxide-semiconductor (CMOS) circuit. The investigation exhibits that the circuit can effectively reconfigure the circuit with/without rectifying ability, and can process alternating current (AC) signals with the frequency prior 1 KHz and reconfiguration speed up to 25 μs. We also achieve the reconfigurable rectifier circuit memory via complementary semi-floating gate FETs configuration. The complementary configuration here should be of low output impedance and low static power consumption, being beneficial for effective voltage output and large-scale integration.