Enhanced Photoresponse of High Crystalline Bi₂Se₃ Thin-Films Using Patterned Substrates

High-quality Bi₂Se₃ thin films with topological insulating properties at room temperature have recently attracted much attention as one of the promising materials for realizing innovative electronic and optoelectronic devices. Here, we report the high crystallinity growth of Bi₂Se₃ thin films on a patterned sapphire substrate (PSS) by using a vapor-phase transport deposition with minimizing thermal dissociation of Se atoms vaporized in Bi₂Se₃ powder. This PSS not only reduces the large dislocation of heterogeneously grown Bi₂Se₃ on a sapphire substrate but also induces enhanced light absorption in the visible to near-infrared (IR) ranges compared to Bi₂Se₃ on planar sapphire substrates. Thus, the Bi₂Se₃ thin film laterally grown on the PSS reveals uniform surface properties and high crystallinity in the rhombohedral lattice phase with a full width at half maximum of 0.06° for the XRD (003) peak. Also, the photoresponse of the fabricated IR conversion device using Bi₂Se₃/PSS heterostructure exhibits excellent performance and high reliability with no degradation after continuous switching. As a result, the device constructed with the Bi₂Se₃/PSS exhibits one order of magnitude higher NIR induced-photocurrent and 1-2 orders of magnitude faster photo-switching than that with Bi₂Se₃/Al₂O₃. Such an enhancement in the device performance of Bi₂Se₃/PSS is confirmed by the increased absorption spectra in visible and NIR ranges and the improved light absorption distribution.