2D Bi2O2Se: An Emerging Material Platform for the Next-Generation Electronic Industry

Silicon has been the dominant semiconductor for the microelectronics industry since the late 1950s. Following Moore's law, silicon-based integrated circuit (IC) technology evolved into a 5 nm node by the end of 2020. However, silicon-based electronics face various challenges such as reduced carrier mobility and increased short-channel effects at sub-10 nm nodes. To overcome these drawbacks, two-dimensional (2D) semiconductors are among the most competitive candidate materials for next-generation electronics, due to their intrinsic atomic thickness, flexibility, and dangling-bond-free surfaces. Among all the 2D semiconductors, an air-stable and high-mobility 2D Bi2O2Se semiconductor, a novel ternary material, has some prominent advantages that make it particularly favorable in the electronics industry. First, it demonstrates ultrahigh carrier mobility, moderate band gap, outstanding stability, and excellent mechanical properties. Second, it can react with oxygen plasma or oxygen at elevated temperatures to form a high-kappa native oxide Bi2SeO5. The native oxide Bi2SeO5 forms an atomically sharp interface with Bi2O2Se and can directly serve as a gate dielectric. Bi2O2Se is also embodied with some interesting physical properties such as strong spin-orbit coupling, dimerized selenium vacancies, and ferroelectricity. Taking advantage of these properties, researchers have fabricated high-performance electronic devices, including logic devices, optoelectronics, thermoelectrics, sensors, and memory devices. In this account, we will systematically review the structure of 2D Bi2O2Se, including its crystal structure, surface structure, point defects, and electronic band structure and how these structures can affect the electron transport in 2D Bi2O2Se. We will then discuss different approaches to synthesize this material including chemical vapor deposition (CVD), metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), and the solution-assisted method. All these methods show great potential in large-scale production. Third, we will discuss how the structure of Bi2O2 Se affects its chemical and physical properties such as chemical reactivity and ferroelectric, piezoelectric, and electromechanical properties. Fourth, we will talk about how to make use of these properties in electronic devices, including field-effect transistors, logic gates, bolometers, photodetectors, thermoelectrics, piezoelectrics, sensors, and memory devices. Finally, we will put forward our idea on how to pattern large-area Bi2O2Se thin films into isolated channel regions and integrate these devices together into full-functioning circuits. We believe that 2D Bi2O2Se is a promising semiconductor, as a great diversity of high-performance 2D Bi2O2Se-based devices have demonstrated. Hopefully, the unique characteristics of 2D Bi2O2Se can provide additional opportunities to complement or replace silicon as the material platform of the next-generation electronics industry. To fill the gap between dreams and reality, there is still much work to be done, especially in large-scale material synthesis and systematic device integration.