Unveiling defect-mediated carrier dynamics in monolayer semiconductors by spatiotemporal microwave imaging
Zhaodong Chu, Chunyuan Wang, Jiamin Quan, Chenhui Zhang, Chao Lei, Ali Han, Xuejian Ma, Hao‐Ling Tang, Dishan Abeysinghe, Matthew Staab, Xixiang Zhang, A. H. MacDonald, Vincent Tung, Xiaoqin Li, Chih‐Kang Shih, Keji Lai
Abstract
monolayers by laser-illuminated microwave impedance microscopy. The diffusion length and carrier lifetime were directly extracted from the spatial profile and temporal relaxation of microwave signals, respectively. Time-resolved experiments indicate that the critical process for photoexcited carriers is the escape of holes from trap states, which prolongs the apparent lifetime of mobile electrons in the conduction band. As a result, counterintuitively, the long-lived photoconductivity signal is higher in chemical-vapor deposited (CVD) samples than exfoliated monolayers due to the presence of traps that inhibits recombination. Our work reveals the intrinsic time and length scales of electrical response to photoexcitation in van der Waals materials, which is essential for their applications in optoelectronic devices.