Visible to near-infrared broadband photodetector employing thin film topological insulator heterojunction (p-TlBiSe₂/n-Si) diode

The work presents a study of quasi-2D thin topological insulator film of TlBiSe₂ and its heterojunction TlBiSe₂/Glass and TlBiSe₂/Si by thermal coating. The vibrational modes were identified in both the heterojunctions using Raman spectroscopy with the identification of the surface phonon mode (SPM) in the TlBiSe₂/Si heterojunction. Ultrafast dynamics were studied for the relaxation dynamics of the charge carriers in these heterojunctions. The study identified the interface phenomenon in the form of charge states (CT) in TlBiSe₂/Si p-n heterojunction. The p-TlBiSe₂/n-Si heterojunction showed good p-n diode characteristics with a rectification ratio under the dark. Its optical response was studied by varying optical power (2.37–3.78 µW) and wavelength (500–1900 nm). It showed excellent photoresponse in the visible to near-infrared (NIR) range which peaks at 900 nm wavelength in both forward as well reverse bias. The explanation of its optical and electrical performance was modeled in terms of band structure, surface states, and interface phenomenon. The study is important in terms of the implementation of next-generation topological insulator-based photodetectors.