Controlled Synthesis of a High‐Mobility Bi3O2.5Se2 Semiconductor by Oxidation of Bi2Se3 for Fast and Highly Sensitive Photodetectors

Abstract

AbstractThe search of new high‐mobility two‐dimensional (2D) semiconductors is crucial for the development of next‐generation photodetectors, since current photodetectors based on single 2D semiconductors usually cannot simultaneously own ultrafast response rate and ultrahigh sensitivity. Here, using a facial method of sequentially oxidizing Bi2Se3 at optimal O content, a series of bismuth oxyselenide semiconductors (Bi3O2.5Se2, Bi2O2Se, Bi2SeO5) with appealing electronic applications are successfully synthesized. The crystal and band structures of a superlattice‐free Bi3O2.5Se2 phase are resolved by 3D electron diffraction and density functional theory calculations, showing a unique non‐neutral layered structure, moderate band gap, and small effective mass. More importantly, the concept of Bi2Se3 + O2 can be extended to synthesize the superlattice‐free Bi3O2.5Se2 ultrathin films by chemical vapor deposition, whose room‐temperature mobility can be as high as ≈150 cm2 V−1 s−1 based on Hall measurements. The ultrathin Bi3O2.5Se2 photodetectors with a simple device configuration simultaneously own ultrafast response time (≈31 µs), ultrahigh responsivity (≈8 × 104 A/W), and large detectivity (≈8 × 1013 Jones). This work not only introduces a facile way to regulate the phase in the bismuth oxyselenide family, but also provides an alternative candidate for ultrafast and ultrasensitive photodetectors.