Electronic and optical characteristics of Silicane/GeAs van der Waals heterostructures: Effects of external electric field and biaxial strain: A first-principles study

Abstract

The van der Waals heterostructure offers unusual physical properties to design novel structures for efficient optoelectronic applications. To enhance the low mobility of monolayer SiH and broaden the light absorption coefficient and range of monolayer SiH, a lattice-matched SiH/GeAs vdWh has been constructed. At the same time, the basic electronic and optical properties were investigated by first-principles calculations. The SiH/GeAs vdWh with six different structural configurations were compared, and the most stable configuration model H2 has a type-II band alignment with an indirect bandgap semiconductor value of 1.54 eV. It is associated with a strong charge transfer. Moreover, SiH/GeAs vdWh possesses anisotropic transport properties with high electron mobility along the y-direction. Interestingly, both external electric field and biaxial strain can adjust band offsets and bandgaps values. After applying vertical electric fields, The SiH/GeAs vdWh has a mutual transformation from type-I (symmetric) to type-II(staggered) to type-III(broken) band alignment, and metal-semiconductor phase transitions occurred at −0.35 and 0.15 V/Å. Besides, it's found that band alignment transition from type-II to type-I emerged under the in-plane biaxial strain of 2% and transformed indirect into direct bandgap. More importantly, tensile biaxial strain can enhance the visible-light absorption while sustaining type-II band alignment, which is favorable for photocatalysis of visible light. Our results indicate that the SiH/GeAs vdWh's moderate bandgap, excellent transport properties and optical performance may have potential applications in the field of nanoelectronic and optoelectronic devices.