Manipulation of Photoresponse via Defect-Level Excitations in Metal-Insulator-Semiconductor-Type Two-Dimensional Heterostructure for Optoelectronic Logic Gates.

In recent years, effective carrier-exciton conversion and defect engineering in tunneling diodes based on metal-insulator-semiconductor (MIS) van der Waals heterostructures have attracted extensive research interest in modulating optoelectronic device performance. Effectively exciting and controlling defects in such devices, thereby enabling tunable optoelectronic responses, is critical for both functional realization and performance enhancement. Here, we report a MIS heterostructure photodetector consisting of monolayer graphene (Gr), hexagonal boron nitride (h-BN), and monolayer molybdenum disulfide (MoS2). Defect states within h-BN layers are successfully activated, allowing controlled interlayer charge transfer among the two-dimensional materials. Under visible-light illumination, the device reveals a wavelength-selective photoresponse at 405 and 638 nm. The mechanism underlying the selective photocurrent generation is elucidated through defect-state modeling of h-BN combined with energy-band alignment analysis. Notably, the device demonstrates a high switching ratio of up to 105 and an ultrafast response time of approximately 7-8 μs. These characteristics enable the demonstration of its potential for applications such as raster-scanned photocurrent imaging and optoelectronic logic operations.