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

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 Vds = 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.