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.