Charge transfer induced symmetry breaking in GaN/Bi₂Se₃ topological heterostructure device

In topological insulators (TI) for surface electron transport, dissipationless surface states are required and are activated by symmetry breaking usually by reducing thickness of the film. Substrates play an important role in modulating the surface properties by modifying the surface electronic and mechanical properties. In the present work, we have studied the n-GaN/p-Bi₂Se₃ topological heterojunction for the topological surface states and analyzed by Raman and ultrafast transient absorption (TA) spectroscopy probed in visible and NIR regions. Raman spectrum clearly shows the electron-phonon interaction at the surface by appearance of surface phonon modes (SPM) in heterojunction. TA spectroscopy is performed on Glass/Bi₂Se₃ and n-GaN/Bi₂Se₃ heterojunction to identify surface states, energy levels, charge transfer and carrier relaxation processes. Electrical measurements under dark and illuminated conditions were performed for deeper understanding of the interface states and their effect on electrical and optical performance. The study provides complete understanding of n-GaN/TI-based interfaces by spectroscopic and electrical measurements for their application in next-generation electronic and optical devices.