Dual Probe Optical and Electrical Investigation of Ultrafast Electron–Phonon Interaction in Bi₂Se₃/ZnSe Heterostructures

Understanding the interplay between electron and phonon dynamics in heterostructures is critical for optimizing their optoelectronic properties. Despite the extensive study of Bi2Se3 as a topological insulator and ZnSe as a wide-band gap semiconductor, the dynamics of electron–phonon interactions in their heterostructures remain underexplored. In this work, we perform a dual-probe investigation (optical and electrical approach) of Bi 2 Se 3 /ZnSe and ZnSe/Bi 2 Se 3 heterostructure configurations. We have fabricated vdW heterostructures with varying symmetries, including Bi 2 Se 3 /ZnSe and ZnSe/Bi 2 Se 3 configurations. The photoresponse in ZnSe and its vdW HSs is observed across the visible to near-infrared (NIR) range (355, 532, and 1064 nm). Compared to intrinsic ZnSe, the Bi 2 Se 3 /ZnSe heterostructure exhibits an increase in photocurrent from ∼50 to ∼1150 μA, reflecting a remarkable enhancement, while the ZnSe/Bi 2 Se 3 heterostructure shows an increase to ∼280 μA, achieving improvement. Furthermore, the rise time of vdW heterostructures (69.05 ms) is significantly faster than that of intrinsic ZnSe (98.7 ms), showing an improvement of ∼30%. Charge carrier dynamics and charge transfer mechanisms, revealed through ultrafast spectroscopy, provide key insights into interfacial interactions. This study highlights the role of vdW interfaces in tuning charge transport and phonon interactions, paving the way for advanced optoelectronic applications, including photodetectors, spintronic devices, and quantum technologies.