Two-Dimensional Phototransistors with van der Waals Superstructure Contacts for High-Performance Photosensing

High Resolution Image Download MS PowerPoint Slide Semiconducting transition metal dichalcogenides (TMDs) possess exceptional photoelectronic properties, rendering them excellent channel materials for phototransistors and holding great promise for future optoelectronics. However, the attainment of high-performance photodetection has been impeded by challenges pertaining to electrical contact. To surmount this obstacle, we introduce a phototransistor architecture, in which the WS 2 channel is connected with an alternating WS 2 –WSe 2 strip superstructure, strategically positioned alongside the source and drain contact regions. Illumination triggers efficient separation of photoexcited electrons and holes due to the type-II staggered band alignment within the superstructure. Consequently, the contact regions exhibit degenerately doped n + WS 2 and p + WSe 2 strips under light illumination, resulting in minimal contact resistivity with the metal electrodes. The resultant WS 2 phototransistor exhibits a remarkable responsivity of 2.4 × 10 6 mA/W and an impressive detectivity of 2.6 × 10 12 Jones. Furthermore, our time-resolved measurements reveal the absence of persistent photoconductance. This proposed phototransistor architecture provides a route for high-performance photodetection, effectively surpassing previous limitations associated with electrical contact.