High-performance photodetector and its optoelectronic mechanism of MoS2/WS2 vertical heterostructure

Highlights: • The MoS₂/WS₂ vertical heterostructure is successfully prepared by the transfer method. • High on/off ratio (near 10⁸) and electron mobility (12 cm²V^-1S^-1) of MoS₂/WS₂ heterostructure photodetector are achieved. • The MoS₂/WS₂ photodetector exhibits both photoresponsivity of 298 A/W and photoresponse speed of 9 ms simultaneously. Two-dimensional heterostructures based on transition metal dichalcogenides (TMDCs) exhibit enhanced electrical and optoelectrical properties, which are promising for next-generation optoelectronics devices. In this work, we demonstrate the preparation of MoS₂/WS₂ vertical heterostructure and investigate their photoresponse properties by fabricating n-type photodetectors with titanium (Ti) as source-drain electrode. Uniform MoS₂ and WS₂ films are synthesized on SiO₂/Si substrates by chemical vapor deposition (CVD) method respectively, and then MoS₂/WS₂ vertical heterostructures are achieved via transferring MoS₂ onto WS₂ films. The WS₂- and MoS₂-based devices exhibit on/off ratio and electron mobility of 10⁶, 0.03 cm²V^-1S^-1 and > 10⁶, 2.6 cm²V^-1S^-1 at V_ds = 6 V. Notably, the MoS₂/WS₂ heterostructure photodetector achieves on/off ratio of near 10⁸ and electron mobility of 12.6 cm²V^-1S^-1, which is higher than that of pure WS₂ and MoS₂ devices. The photodetector based on MoS₂/WS₂ heterostructure shows enhanced optoelectronic performance with photoresponsivity of 298 A/W and specific detectivity of 2.38 × 10¹¹ Jones under 405 nm laser with the power density of 0.09 mW/cm². Simultaneously, fast photoresponse speed of 9 ms is obtained owing to the speed of separating and recombining electron-hole pairs. The photodetectors exhibit excellent stability and repeatability to laser, which provides more possibilities for future electronic and optoelectronic applications.