Prediction of two-dimensional C₃N₂ semiconductors with outstanding stability, moderate band gaps, and high carrier mobility

Two-dimensional (2D) semiconductors with suitable band gaps, high carrier mobility, and environmental stability are crucial for applications in the next generation of electronics and optoelectronics. However, current candidate materials each have one or more issues. In this work, two novel C₃N₂ monolayers, P-C₃N₂ and I-C₃N₂ are proposed by first-principles calculations. Both structures have demonstrated excellent dynamical and mechanical stability, with thermal stability approaching 3000 K. Importantly, P-C₃N₂ shows a distinct advantage in formation energy compared to currently synthesized 2D carbon nitride materials, indicating its potential for experimental synthesis. Electronic structure calculations reveal that both P-C₃N₂ and I-C₃N₂ are intrinsic semiconductors with moderate band gaps of 2.19 and 1.81 eV, respectively. Additionally, both C₃N₂ monolayers display high absorption coefficients up to 10⁵ cm^-1, with P-C₃N₂ showing significant absorption capabilities in the visible light region. Remarkably, P-C₃N₂ possesses an ultra-high carrier mobility of up to 10⁴ cm² V^-1 s^-1. These findings provide theoretical insights and candidates for future applications in the electronics and optoelectronics fields.