Electrical and optical properties of SnS$_{\mathrm{2}}$/WSe$_{\mathrm{2}}$ van der Waals Heterojunction FETs

Two dimensional crystals based on atomically thin films of transition metal dichalcogenides offer an exciting platform for various optoelectronic applications. Their unique crystal properties make them particularly attractive for van der Waals heterostructures which open up an additional degree of freedom to tailor the material properties into new physics and device applications. In this work, we explore, for the first time, the optoelectronic properties of van der Waals SnS$_{\mathrm{2}}$/WSe$_{\mathrm{2}}$ heterojunction. WSe$_{\mathrm{2}}$ is an ambipolar semiconductor while SnS$_{\mathrm{2}}$ is an $n$-type wide bandgap semiconductor. We use the pickup and dry transfer methods to fabricate SnS$_{\mathrm{2}}$/WSe$_{\mathrm{2\thinspace }}$heterojunction transistors (hetero-FETs). We observe negative differential transconductance in the SnS$_{\mathrm{2}}$/WSe$_{\mathrm{2}}$ hetero-FET. Also, the heterostructure couples strongly to incident light and shows high photovoltaic responsivity which can find applications in nano-devices such as photo-detectors and solar cells.