▎ 摘 要
A self-driven photosensor with signal-reversal response has the potential to work as a photodetector in complex environments with multiple signals owing to better signal recognition and enhanced signal-processing efficiency. Herein, a metal-semiconductor-metal photodetector based on ambipolar WSe2 with two electrodes comprising two-dimensional (2D) van der Waals (vdWs) metal Fe3GeTe2 and semimetal graphene was proposed to form an asymmetrical metal-contacted architecture with different Schottky barrier heights. The regulating gate field-induced Fermi level shift in WSe2 can be used to manipulate the WSe2 channel's carrier type, resulting in a polarity-reversible photodetector without a bias voltage. Furthermore, the photovoltaic effect can be observed from wavelengths of 450 nm (visible) to 850 nm (infrared) without external voltage. The large open voltage is -0.177 V and short-circuit current is 17 nA under a 650-nm excitation wavelength. The reported WSe2-based photodetector exhibits excellent properties under zero bias, including a large photo-to-dark current ratio greater than 10(6) with dark current less than 1 fA, photovoltaic performance with an external quantum efficiency of 27.14%, an excellent detectivity of 3.4x10(10) Jones, and a high responsivity of 116.38 mA/W. Rapid electron transfer occurs at the interface between WSe2 and vdWs electrodes, resulting in a 370-mu s response speed owing to the clean and nondestructive interfaces between vdWs metals and WSe2. This study demonstrates the wide application prospect of the vdWs metal Fe3GeTe2 as an electrode forming a Schottky junction for realizing a photodetector without an external voltage and accelerates the development of 2D photosensors with various working modes.