Spectromicroscopy and imaging of photoexcited electron dynamics at in-plane silicon pn junctions.

Nanoscale

State Key Laboratory for Mesoscopic Physics, Collaborative Innovation Center of Quantum Matter, Nano-optoelectronics Frontier Center of the Ministry of Education, School of Physics, Peking University, Beijing 100871, China. and Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China and Peking University Yangtze Delta Institute of Optoelectronics, Nantong 226010, Jiangsu, China.

Published: February 2021

The ultrafast spatiotemporal imaging of photoexcited electrons is essential to understanding interfacial electron dynamic processes. We used time- and energy-resolved photoemission electron microscopy (PEEM) to investigate the photoexcited electron dynamics at multiplex in-plane silicon pn junctions. We found that the measured kinetic energy of photoelectrons from n-type regions is higher than that from p-type regions owing to different work functions. Interestingly, the kinetic energy of outer n-type regions is higher than that of inner n-type regions, which is caused by the reverse bias induced by photoemission. Time-resolved PEEM results reveal different evolution rates of hot electrons in different doping regions. The rise time of the n-type (outer n-type) regions is faster than that of the p-type (inner n-type) regions. So, closed doping patterns can influence the electron spectra and dynamics at the micro-nano scale. These results help us to understand the ultrafast dynamics of carriers at in-plane interfaces and optimize optoelectronic integrated devices with complex heterojunctions.

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http://dx.doi.org/10.1039/d0nr07954eDOI Listing

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