2D Reconfigurable van der Waals Heterojunction for Logic Gate Circuits and Wide-Spectrum Photodetectors via Sulfur Substitution and Band Matching

The attractive physical properties of two-dimensional (2D) semiconductors in group IVA-VIA have been fully revealed in recent years. Combining them with 2D ambipolar materials to construct van der Waals heterojunctions (vdWHs) can offer tremendous opportunities for designing multifunctional electronic and optoelectronic devices, such as logic switching circuits, half-wave rectifiers, and broad-spectrum photodetectors. Here, an optimized SnSe_0.75S_0.25 is grown to design a SnSe_0.75S_0.25/MoTe₂ vdWH for logic operation and wide-spectrum photodetection. Benefiting from the excellent gate modulation under the appropriate sulfur substitution and type-II band alignment, the device exhibits reconfigurable antiambipolar and ambipolar transfer behaviors at positive and negative source–drain voltage (V_ds), enabling stable XNOR logic operation. It also features a gate-modulated positive and negative rectifying behavior with rectification ratios of 265:1 and 1:196, confirming its potential as half-wave logic rectifiers. Besides, the device can respond from visible to infrared wavelength up to 1400 nm. Under 635 nm illumination, the maximum responsivity of 1.16 A/W and response time of 657/500 μs are achieved at the V_ds of −2 V. Furthermore, due to the strong in-plane anisotropic structure of SnSe_0.75S_0.25-alloyed nanosheet and narrow bandgap of 2H-MoTe₂, it shows a broadband polarization-sensitive function with impressive photocurrent anisotropic ratios of 15.6 (635 nm), 7.0 (808 nm), and 3.7 (1310 nm). The direction along the maximum photocurrent can be reconfigurable depending on the wavelengths. These results indicate that our designed alloyed SnSe_0.75S_0.25/MoTe₂ vdWH has reconfigurable logic operation and broadband photodetection capabilities in 2D multifunctional integrated circuits.