Van der Waals heterojunctions with negative differential transconductance for broadband photodetection, multi-valued logic, and artificial neuron

Negative differential transconductance (NDT) presents a promising platform for advancing next-generation computing technologies by reducing power consumption without increasing circuit complexity. The realization of multi-valued logic computing depends on developing innovative device concepts and circuits beyond conventional complementary metal oxide semiconductor (CMOS) technology. In this study, we demonstrate NDT behavior in an InSe/BP heterojunction at room temperature, achieving a tunable NDT with a remarkable peak-to-valley current ratio of 43.5 at V_ds = 1.4 V. The device also exhibits distinct photovoltaic behavior and a broad spectral response spanning from 520 to 1550 nm. It delivers excellent photodetection performance, with a high photoresponsivity of 561.68 A W⁻¹, detectivity of 3.95 × 10¹² cmHz^1/2 W⁻¹, an ultrahigh external quantum efficiency (EQE) of 1341.87%, and a fast response speed of 27 μs under 532 nm illumination. Even in the near-infrared regime of 1550 nm, the device maintains a responsivity of 2.21 A W⁻¹, detectivity of 1.23 × 10¹⁰ cmHz^1/2 W⁻¹, and a rise time of 477 μs. Furthermore, we successfully implemented a ternary inverter, a key component for multi-valued logic computing technology, and an artificial neuron capable of emulating neural signal transmission. This study not only highlights the exceptional electronic and optoelectronic performance of the device but also provides deeper insights into band modulation, paving the way for future advancements in low-power, high-speed logic, and neuromorphic applications. (Figure presented.).