Ultrafast charge transfer and optoelectronic performance of n−InSe/m−SnS (GeSe) van der Waals heterostructures

Two-dimensional van der Waals heterostructures (vdWHs) are promising candidates for multi-functional electronic and optoelectronic devices. Here, based on reconfigurable band alignment, we design $n\text{\ensuremath{-}}\mathrm{InSe}/m\text{\ensuremath{-}}\mathrm{SnS}$ (GeSe) multilayer vdWHs with different layer combinations to explore their ultrafast dynamic process and optoelectronic device performance. When $n>1(3)\mathrm{L}$, the band structure transforms from staggered- into broken-gap band alignment, and increasing the layer number can effectively widen the band-to-band tunneling window to achieve adjustable tunneling field-effect transistors. For the type-II InSe/GeSe vdWHs, the ultrafast electron transfer timescale reduces from 95 to 33 fs when the InSe layer number increases from 1L to 2L. Moreover, the photocurrent density of $n\text{\ensuremath{-}}\mathrm{InSe}/m\text{\ensuremath{-}}\mathrm{SnS}$ (GeSe) multilayer vdWHs photodetectors can be significantly improved with layer-combination modulation, and the value of 2-InSe/1-GeSe vdWHs can be approximately increased by 12 times compared with that of 1-InSe/1-GeSe vdWHs. This research provides an effective way to design tunneling field-effect transistors and photodetectors in low-power consumption and high-speed switching.