Revealing Bipolar Photoresponse in Multiheterostructured WTe2–GaTe/ReSe2–WTe2 P–N Diode by Hybrid 2D Contact Engineering

The van der Waals (vdW) heterostructures based on two-dimensional (2D) semiconducting materials have been thoroughly investigated with regard to practical applications. Recent studies on 2D materials have reignited attraction in the p–n junction, with promising potential for applications in both electronics and optoelectronics. 2D materials provide exceptional band structural diversity in p–n junction devices, which is rare in regular bulk semiconductors. In this article, we demonstrate a p–n diode based on multiheterostructure configuration, WTe₂–GaTe-ReSe₂–WTe₂, where WTe₂ acts as heterocontact with GaTe/ReSe₂ junction. Our devices with heterocontacts of WTe₂ showed excellent performance in electronic and optoelectronic characteristics as compared to contacts with basic metal electrodes. However, the highest rectification ratio was achieved up to ∼2.09 × 10⁶ with the lowest ideality factor of ∼1.23. Moreover, the maximum change in photocurrent (I_ph) is measured around 312 nA at V_ds = 0.5 V. The device showed a high responsivity (R) of 4.7 × 10⁴ m·AW^–1, maximum external quantum efficiency (EQE) of 2.49 × 10⁴ (%), and detectivity (D*) of 2.1 × 10¹¹ Jones at wavelength λ = 220 nm. Further, we revealed the bipolar photoresponse mechanisms in WTe₂–GaTe-ReSe₂–WTe₂ devices due to band alignment at the interface, which can be modified by applying different gate voltages. Hence, our promising results render heterocontact engineering of the GaTe–ReSe₂ heterostructured diode as an excellent candidate for next-generation optoelectronic logic and neuromorphic computing.