Gate controlled wide bandwidth WSe2/SnSe2 heterostructure photodetectors
Yu-Hsuan Lu1*, I. Y. Chen2, L. C. Li4, Y. F. Lin3, T. S. Lim5, C. H. Wu1, D. Y. Lin6, Y. W. Suen2,3
1Graduate Institute of Electronics and Engineering, National Taiwan University, Taipei, Taiwan
2Institute of Nanoscience and Nanotechnology, National Chung Hsing University, Taichung, Taiwan
3Department of Physics, National Chung Hsing University, Taichung, Taiwan
4Center for Nano Science and Technology, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
5Department of Applied Physics, Tunghai University, Taichung, Taiwan
6Department of Electronic Engineering, National Changhua University of Education, Changhua, Taiwan
* Presenter:Yu-Hsuan Lu,
We report the fabrication and electrical properties of tunnel field-effect transistors (TFETs) based on multilayer Van der Waals SnSe2/WSe2 heterojunctions. The dry transfer method was used to stack a SnSe2 flake picked up by a PDMS stamp onto a WSe2 flake on a Si substrate covered by a 300 nm thick SiO2 film. Both layered materials were obtained by the mechanical exfoliation method. The 30/70 nm Ti/Au electrodes were defined by e-beam lithography. The multilayer SnSe2 is n-type for most back gate biases, while WSe2 is bipolar [1]. Charge transfer from SnSe2 to WSe2 occurs in the overlapping region, resulting in the energy band bending near the interface. Meanwhile, the carrier concentration in the overlapping region differs from the region without overlapping, causing the energy band to shift upward along the normal direction of WSe2 Layer. Near the boundary of the overlapping area, the energy band bends in the lateral direction. Scanning photocurrent microscopy (SPCM) using a 633 nm laser with a spot size of 1.5 um2 is applied to measure the photocurrent distribution in the devices. A spectrometer is used to analyze the absorption spectra under different gate and source-drain biases. The SPCM data and the absorption spectra can be explained by the proposed energy band diagrams. This study demonstrates that SnSe2/WSe2 heterojunction devices may have excellent optoelectronic performance, giving a promise for potential applications in photodetector and photovoltaic devices.

Keywords: tunnel field-effect transistors, SnSe2, WSe2