First-principles insights into Bi2XO5 (X = Se, Te) monolayers as high-k gate dielectrics for 2D electronics

Scaling silicon-based transistors to sub-ten-nanometer technology nodes presents significant challenges due to the difficult in achieving both atomic-scale thickness and excellent tunneling performance simultaneously. In this work, we employed first-principles calculations to investigate the dielectric properties of two recently reported van der Waals layered materials, Bi2SeO5 and Bi2TeO5. Our results reveal that Bi2SeO5 and Bi2TeO5 monolayers exhibit out-of-plane dielectric constant of 15.2 and 7.6, respectively, with in-plane dielectric constant reaching as high as 39.0 and 26.0. To evaluate their potential as gate dielectrics, we calculated the band offsets and equivalent oxide thicknesses (EOTs) of Bi2SeO5 and Bi2TeO5 monolayers. The results show that both materials exhibit favorable band offsets relative to silicon and transition-metal dichalcogenide channel materials, along with low EOT. Finally, we estimated the dielectric leakage current density utilizing Bi2SeO5 and Bi2TeO5 based on a p-doped silicon-channel transistor, predicting a low leakage current (<10−8 A cm−2). Our study provides theoretical insights into the potential application of bismuth selenite and bismuth tellurite monolayers as gate dielectrics in two-dimensional electronics.