Experimental photodetector dynamically switches working modes for high performance

In recent years, 2D layered transition metal dichalcogenides (TMDs) have shown promise for easily fabricated and versatile photodetectors. Current TMDs, however, cannot be operated to be highly responsive while also featuring high detectivity. New work looks to provide one of the first working prototypes of such a dual-mode photodetector.

Luo et al. present the results from a experimental photodetector capable of dynamically switch its working mode, allowing for a device with both high detectivity and high responsivity. By stacking a tungsten diselenide (WSe₂) flake with a phase-transition material, vanadium dioxide (VO₂), the group’s device can change from a type II p-n heterojunction to a Schottky junction as the VO₂ layer undergoes an insulator-to-metal transition.

“The big changes of electrical, optical, and structural constants during its insulator-to-metal transition have the VO₂ ideally function as an active substrate to modulate the properties of other materials, like 2D-layered TMDs,” said author Kai Liu. “It is also easy to trigger the transition of VO₂ as its insulator-to-metal transition temperature is slightly above room temperature.”

Combining the p-type arrangement of the tungsten diselenide with the n-type arrangement of VO₂ provides the device with better band alignments for charge separation than type-I materials used in many current optoelectronic applications.

While the VO₂ component is insulated, device yields self-driven and energy efficient photodetectivities as high as 1.87×10¹³ Jones. After VO₂ transition to its metallic state, the heterojunction exhibits a large photoresponsivity of 6.6 A W⁻¹ at a low bias of 0.5 V.

Liu hopes the group’s work inspires more work into such heterojunctions. They next look to explore other combinations of materials to create heterojunctions with more functions.

Source: “Phase-transition modulated, high-performance dual-mode photodetectors based on WSe₂/VO₂ heterojunctions,” by Hao Luo, Bolun Wang, Enze Wang, Xuewen Wang, Yufei Sun, Qunqing Li, Shoushan Fan, Chun Cheng, and Kai Liu, Applied Physics Reviews (2019). The article can be accessed at https://doi.org/10.1063/1.5124672 .