Ferroelectric-tuned van der Waals heterojunction with band alignment evolution

Abstract Van der Waals (vdW) integration with abundant two-dimensional materials provides a broad basis for assembling functional devices. However, band alignment in a specific vdW heterojunction (VHJ) is difficult to tune, restricting its multifunctionality and structural simplicity. Here, we designed a ferroelectric-tuned VHJ (Fe-VHJ) device structure by integrating a GeSe/MoS2 VHJ and poly (vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE))-based ferroelectric polymer. An ultrahigh electric field derived from the ferroelectric polarization that can effectively modulate the band alignment of the GeSe/MoS2 heterojunction. Band alignment transition of the heterojunction from type II to type I was demonstrated. The combination of anisotropic GeSe with MoS2 realised a high-performance polarization-sensitive photodetector exhibiting low dark current of approximately 1.5 pA, quick response of 14 μs, and high detectivity (D*) of 4.7 × 1013 Jones. Dichroism ratios were also enhanced by ferroelectric polarization in a broad-spectrum from visible to near-infrared. The GeSe/MoS2 Fe-VHJ has great potential for multifunctional detection applications in sophisticated light information sensing. More profoundly, the Fe-VHJ structure provides a valid band-engineering approach to creating versatile devices.