Prediction of Two-Dimensional Semiconductor Compounds Man3 (M = V, Nb, Ta; a = Si, Ge) from Ma2n4 Family

Two-dimensional (2D) materials, renowned for their excellent structural and electronic properties, are considered to be the best candidates in the post-Moore era. Herein, we successfully designed 22 stable 2D monolayers with built-in electric fields based on the design principle of valence charge balance and layer stacking. The predicted novel monolayers, i.e., 2D MAN3, originates from the MA2N4 (M = V, Nb, Ta; A = Si, Ge), which has been widely studied in recent years. All these monolayers exhibit semiconductor properties, covering a wide range band gaps from 1.23 to 3.14 eV, with half displaying a direct band feature. Based on the modified carrier mobility calculation method, we found that the MAN3 monolayer shows remarkable hole mobility, reaching up to 104 cm2V-1s-1. Owing to their wide range of band gaps, 2D MAN3 has excellent optical absorption in the infrared, visible, and ultraviolet regions. Additionally, due to their non-centrosymmetric structure, these monolayers possess intrinsic built-in electric fields that can effectively adjust the band edges, which not only facilitates the construction of different types of interface contacts, but also satisfies the requirements of photovoltaic water splitting. Our work not only significantly expands the MAN3 family, but also provides valuable insights for future research.