Unveiling Electric Bias Effects on Ultrafast Carrier Dynamics in Multiple Stacked ZnTe/Bi₂Te₃ Heterostructures

Abstract

van der Waals (vdW) heterostructures (HS) of topological materials with transition-metal chalcogenides are gaining attention due to their unique electrical and optical properties. However, studies mainly focus on single-stacked vdW HS; investigating multiple stacked heterostructures could yield significant insights in this domain. Here, we investigated the electric bias-induced carrier dynamics and photoconductive behavior in multiple stacked vdW HS composed of ZnTe and Bi 2 Te 3 . The photodetective performance of 4-layered vdW HS is substantially higher than that of 2-layered vdW HS, and the response time of 4-layered vdW HS (710 ms) is also shorter than that of 2-layered vdW HS (840 ms) because of enhanced optical absorption, more carrier separation at the interface, and carrier mobility. Moreover, electrical bias-dependent transient reflectance spectroscopy reveals that due to the external electric field, the Fermi-level modulation and variation in concentration of Dirac electrons influence the band positions in TR spectra. Furthermore, we hypothesized that applied bias can distort the lattice and increase electron−phonon coupling, potentially altering the charge transfer process. This research provides valuable insights into the intricate charge transport mechanisms within multiple stacked vdW HS, laying a solid foundation for future research in materials science and optoelectronics.