Growth of Vertical Heterostructures Based on Orthorhombic SnSe/Hexagonal In2Se3 for High-Performance Photodetectors
Vertical heterostructures based on two-dimensional (2D) layered materials are ideal platforms for electronic structure engineering and novel device applications. However, most of current heterostructures focus on layered crystals with a similar lattice. And the heterostructures made by 2D materials with different structures are rarely investigated. In this work, we succeed in fabricating vertical heterostructures by combining orthorhombic SnSe/hexagonal In2Se3 vertical heterostructures using a two-step physical vapor deposition (PVD )method. Structural characterization reveals that the heterostructures are formed by vertically stacking SnSe on the top of In2Se3 film and vertical heterostructures possess high quanlity, which In2Se3 exposed surface is (0001) plane and SnSe prefer growing along the  direction. Raman maps confirm the precisely spatial modulation of the as-grown SnSe/In2Se3 heterostructures. Additionally, high-performance photodetectors based on the vertical heterostructures have been fabricated directly on the substrate, showing broadband response, reversibility and stability. Compared with dark current, the device demonstrates one order magnification of photocurrent, about 186 nA, under 405nm laser illumination and power of 1.5 mW. Meanwhile device demonstrates an obvious increase for changing incident laser power, where Iph ∝ P0.7. Also device demonstrates a high responsivity of up to 350 mA/W and a fast response time about 139 ms. This work broadens the horizon of the synthesis and application of vertical heterostructures based on 2D layered materials with different structures and further develops exciting technologies beyond the reach of the existing materials.