Direct oxidation pathways for creating the high-κ native oxide on semiconducting Bi₂O₂Se films

Tai-Ting Lee^1,2*, Mei-Yin Chou^1,2

¹Department of Physics, National Taiwan University, Taipei, Taiwan
²Institute of Atomic and Molecular Sciences, Academic Sinica, Taipei, Taiwan

* Presenter:Tai-Ting Lee, email:a6240306@gmail.com

With the goal of scaling down semiconductor devices, two-dimensional (2D) semiconductors have become potential candidate materials in modern electronics. A defect-free, atomically matched interface between the gate oxide and the channel material is crucial for a high-performance device. However, this makes most 2D materials that have been considered so far less competitive compared to traditional three-dimensional (3D) devices due to their lack of a native gate oxide. Recently, it was discovered that an air-stable and thin-film semiconducting material, Bi₂O₂Se, can form high-κ native oxide layers with the assistance of UV light, thus preserving high mobility in transistors. The native oxide of Bi₂O₂Se can be categorized into two phases: α-Bi₂SeO₅ and β-Bi₂SeO₅ resulting from distinct oxidation pathways. In this study, we investigate the structural evolution from semiconducting Bi₂O₂Se into the native oxide Bi₂SeO₅. The formation of the α-phase oxide is facilitated by a 'channel' plane on the surface of Bi₂O₂Se, while the β-phase forms through intercalative oxidation. Both processes can proceed in a layer-by-layer fashion. Furthermore, we have identified an energetically favorable β-Bi₂SeO₅ structure by first-principles calculations and found a type-I band alignment at the β-Bi₂SeO₅/Bi₂O₂Se interface, consistent with the experimentally observed good gate insulation properties.

Keywords: high-κ native oxide, large band offsets, first-principles calculations