Fig. 2: Optoelectronic characterization of the vertical channel photodetector.

a Schematic illustrating the experimental setup of the Gr/BP/MoS₂/Gr vertical channel photodetector. The photocurrent was measured through the top and bottom Au electrodes. A high-resistivity silicon substrate is used to avoid the parasitic capacitance effects caused by the heavily doped silicon substrate. Here, BP and Gr represent black phosphorus and graphene, respectively. V_ds indicate the bias applied between the source and drain. b Optical image of the fabricated vertical device, with the BP, MoS₂, and graphene layers outlined by yellow, blue, and white lines, respectively, for clarity. Inset: Photocurrent map of the device obtained by scanning a focused laser beam with a wavelength of 633 nm and V_ds = 0 V. The area enclosed by the dotted line represents the overlapping region of the BP/MoS₂ heterojunction. c Output characteristics of the vertical photodetector in the dark and under 1550 nm laser illumination at different light powers. d Time-resolved photoresponse at different light powers at a wavelength of 1550 nm with V_ds = 0 V. e Wavelength-dependent time-resolved photoresponse measured at V_ds = 0 V with an incident light power of 7.5 µW. f Power dependence of the photocurrent extracted at V_ds = 0 V for four characteristic spectral bands, namely, the ultraviolet (325 nm), visible (633 nm), near-infrared (1550 nm), and mid-infrared (3200 nm) bands. Here, the dots represent the experiment data, and the lines are the result of fitting the data to a power function. α is an exponent of the power function.