Revealing Bipolar\nPhotoresponse in Multiheterostructured\nWTe<sub>2</sub>–GaTe/ReSe<sub>2</sub>–WTe<sub>2</sub> P–N Diode by Hybrid 2D Contact Engineering

The van der Waals (vdW) heterostructures based on two-dimensional\n(2D) semiconducting materials have been thoroughly investigated with\nregard to practical applications. Recent studies on 2D materials have\nreignited attraction in the p–n junction, with promising potential\nfor applications in both electronics and optoelectronics. 2D materials\nprovide exceptional band structural diversity in p–n junction\ndevices, which is rare in regular bulk semiconductors. In this article,\nwe demonstrate a p–n diode based on multiheterostructure configuration,\nWTe<sub>2</sub>–GaTe-ReSe<sub>2</sub>–WTe<sub>2</sub>, where WTe<sub>2</sub> acts as heterocontact with GaTe/ReSe<sub>2</sub> junction. Our devices with heterocontacts of WTe<sub>2</sub> showed excellent performance in electronic and optoelectronic characteristics\nas compared to contacts with basic metal electrodes. However, the\nhighest rectification ratio was achieved up to ∼2.09 ×\n10<sup>6</sup> with the lowest ideality factor of ∼1.23. Moreover,\nthe maximum change in photocurrent (<i>I</i><sub>ph</sub>) is measured around 312 nA at V<sub>ds</sub> = 0.5 V. The device\nshowed a high responsivity (<i>R</i>) of 4.7 × 10<sup>4</sup> m·AW<sup>–1</sup>, maximum external quantum efficiency\n(EQE) of 2.49 × 10<sup>4</sup> (%), and detectivity (<i>D</i>*) of 2.1 × 10<sup>11</sup> Jones at wavelength λ\n= 220 nm. Further, we revealed the bipolar photoresponse mechanisms\nin WTe<sub>2</sub>–GaTe-ReSe<sub>2</sub>–WTe<sub>2</sub> devices due to band alignment at the interface, which can be modified\nby applying different gate voltages. Hence, our promising results\nrender heterocontact engineering of the GaTe–ReSe<sub>2</sub> heterostructured diode as an excellent candidate for next-generation\noptoelectronic logic and neuromorphic computing.