Asymmetric Joule heating effect on a monolayer MoS₂ device measured by a thermal imaging microscope

Layered transition-metal dichalcogenides (TMDs) materials, which currently provide the most ideal two-dimensional (2D) semiconductor channels, have limited performance due to unavoidable interfacial defects caused by bottom–up processes. These defects act as carrier scattering sources in a 2D channel, causing Joule heat losses. We investigated Joule heating effects on CVD grown monolayer MoS₂ field-effect transistors (FETs) by measuring thermal characteristics according to minute voltage conditions using an infrared (IR) thermal microscope and analyzed it based on the 3D heat transfer simulation. We confirmed that the temperature distribution is non-uniform and maximum temperature of the channel increases due to the asymmetry of the charge distribution when the transistor operated in the saturation mode. The maximum temperature as a function of input power density initially shows the linear relationship and gradually becomes more non-linear as input power increases, and the non-linearity becomes more pronounced at the negative drain-source bias conditions. Our results demonstrate the importance of charge distribution during device operation as well as total input power in thermal analysis studies based on 2D materials.