Characterization of MoS₂/Si and WS₂/Si Heterojunction Photodetectors Fabricated by High-Working Pressure Plasma-Enhanced CVD

Trilayers of MoS₂ and WS₂ were grown on p-type Si wafers using high-working pressure plasma-enhanced chemical vapor deposition technique. Dark current-voltage measurements of the MoS₂/Si and WS₂/Si heterojunctions showed rectifying behaviors, indicating formation of diodes. While illuminating the samples with a green laser (wavelength: 532 nm), both of the heterojunctions exhibited large (negligibly small) photocurrent under reverse (forward) bias conditions. The measured photocurrent was linearly proportional to the laser power at 80 K as well as at room temperature. This suggested that trapping and detrapping of the photo-generated carriers at interface defects and surface adsorbates could not significantly suppress the collection of photo-carriers. We also studied dynamics of photocurrent behaviors using a chopper. Both of the heterojunctions showed fast photoresponse: the rising and decaying time constants were ~ 1 ms. All these results showed that our plasma-enhanced growth technique could be very useful to produce high quality MoS₂/Si and WS₂/Si heterojunctions for optoelectronic applications.