Thickness-Dependent Carrier Recombination Rates of Few-Layer InSe

Ting-Hsuan Wu^1,2*, Hao-Yu Cheng^1,2, Raman Sankar², Kung-Hsuan Lin²

¹Department of Physics, National Taiwan University, Taipei, Taiwan
²Institute of Physics, Academia Sinica, Taipei, Taiwan

* Presenter:Ting-Hsuan Wu, email:wthse0423@gmail.com

Dynamics of carrier recombination is important to understand the physical insight of electronic or optoelectronic devices. However, there is rare work to investigate carrier dynamics of layered materials with different number of layers. In this work, we studied ultrafast carrier dynamics of InSe layers with different thicknesses from ~8 nm to ~44 nm by using time-domain pump-probe spectroscopy. We found that the carrier lifetime of InSe decreases with decreasing thickness. The carrier recombination in few-layer InSe is dominated by surface recombination, and the thickness-dependent lifetimes could be explained by using a free carrier diffusion model with surface recombination velocities. In addition, we found the surface recombination velocities of air-oxidized InSe is lower than those of as-exfoliated InSe. Detailed mechanism will be discussed in the presentation.

Keywords: 2D Layered Material, Surface Recombination, Time-Domain Pump-Probe Spectroscopy, Thickness-Dependent, Surface Oxidation