Interface induced enhancement of THz generation and modulation in hexagonal boron nitride/Si mixed-dimensional van der Waals heterostructure

The interfacial effect in mixed-dimensional van der Waals heterostructure can improve the performance of terahertz (THz) components, such as THz emitter and THz modulator, which highlight the development of THz technology. However, this improvement has only been demonstrated in heterostructure based on graphene or small bandgap two-dimensional materials. We present the enhancement for THz generation and modulation from Si by insulating hexagonal boron nitride (h-BN) layer coating. The surface adsorption charges and the interface trapped charges lower the Fermi energy on Si surface, leading to an enlarged built-in electric field. Consequently, THz generation from h-BN/Si demonstrated significant enhancement compared with that by bare Si surface. Furthermore, the enlarged built-in electric field separates the interface photocarriers and reduces the surface recombination rate. The resulting dense charge accumulation raises up the photoconductivity after optical illumination and the enhanced THz modulation at h-BN/Si interface is approximately ten times higher than that by Si surface. These results not only present an efficient THz generation and modulation from the h-BN/Si interface but also pave the way for the deep understanding of interfacial effect in mixed-dimensional van der Waals heterostructures.