Using Bias-Dependent Photocurrent to Study the Variation of Schottky Barrier Height in MoTe₂/Metal Junctions
K. C. Lee1*, T.-S. Lim2, L. C. Li3, Y. W. Suen1,4
1Department of Physics, National Chung Hsing University, Taichung, Taiwan
2Department of applied physics, Tunghai University, Taichung, Taiwan
3Center for Nano Science and Technology, National Chiao Tung University, Hsinchu, Taiwan
4Institute of Nanoscience and Nanotechnology, National Chung Hsing University, Taichung, Taiwan
* presenting author:Kuo-Chih Lee,
The Schottky barrier height of the contacts in multilayer MoTe₂ thin film field effect transistors (MoTe₂ FETs) was studied by the photocurrent variation as the position of the excitation laser beam spot being swept through the metal-MoTe₂ contacts. The laser beam has a spot size about 1.5 μm and a wavelength of 633 nm. The sample was placed by a two-axis nanometer scanning stage with a 100 X 100 μm² scanning range. The line profile of the photocurrent shows that the strongest photoresponce occurs near the metal-MoTe₂ junction, and the peak intensity varies with the source-drain and backgate biases. From the bias dependence of the photocurrent peak, we can extract the Schottky barrier height. Roughly two types of junctions can be obtained from this analysis: one has a good Schottky barrier with a barrier more than 100 meV; the other is more like an ohmic contact with a barrier smaller than 50 meV. The areal mapping of the photocurrent reveals that the peak photocurrent has a very large fluctuation along the junction line between the metal and MoTe₂, indicating that the barrier height is not uniform even within the same junction.

Keywords: Schottky barrier height, molybdenum ditelluride, photoresponse