Efficient Carrier Separation and Band Structure Tuning of Two-Dimensional C2N/GaTe van der Waals Heterostructure

Efficient carrier separation and suitable band structure are critical for developing better nanoscale optoelectronic devices. However, so far, researchers have not developed a single material system that can satisfy these requirements. Here we design a novel C2N/GaTe van der Waals heterostructure based on the density functional theory. Our results suggest that this heterostructure is an indirect band gap semiconductor (1.39 eV) with intrinsic type-II band alignment, facilitating the separation of photogenerated carriers. Meanwhile, this heterostructure exhibits improved visible optical absorption compared with that of the isolate C2N and GaTe monolayers. More fascinatingly, we find that an intriguing indirect-to-direct band gap semiconductor transition can be induced at the compressive strain of 3%. Simultaneously, the band gaps and carrier effective masses can also be significantly reduced by the biaxial strain. Furthermore, the band edge positions of C2N/GaTe heterostructure can be effectively tuned to straddle the redox potentials of water splitting by isoelectronic anion S and Se substitution at the Te site, and the enhanced optical absorptions are also observed in the doped heterostructures, indicating that S (Se)-doped C2N/GaTe heterostructures are potential photocatalysts for water splitting. In addition, effective spatial separation of photogenerated carriers is expected to occur for all of the above cases. These findings suggest that the C2N/GaTe heterostructure is a promising candidate for application in future nanoelectronics and optoelectronics devices and also provides some valuable information for future experimental research.