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Carrier Density Oscillation in photoexcited Semiconductors

Najafi, Ebrahim and Jafari, Amir and Liao, Bolin and Zewail, Ahmed (2019) Carrier Density Oscillation in photoexcited Semiconductors. . (Unpublished)

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The perturbation of a semiconductor from the thermodynamic equilibrium often leads to the display of nonlinear dynamics and formation of spatiotemporal patterns due to the spontaneous generation of competing processes. Here, we describe the ultrafast imaging of nonlinear carrier transport in silicon, excited by an intense femtosecond laser pulse. We use scanning ultrafast electron microscopy (SUEM) to show that, at a sufficiently high excitation fluence, the transport of photoexcited carriers slows down by turning into an oscillatory process. We attribute this nonlinear response to the electric field, generated by the spatial separation of these carriers under intrinsic and photo-induced fields; we then provide an advection-diffusion model that mimics the experimental observation. Our finding provides a direct imaging evidence for the electrostatic oscillation of hot carriers in highly excited semiconductors and offers new insights into their spatiotemporal evolution as the equilibrium is recovered.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Najafi, Ebrahim0000-0003-3634-9346
Jafari, Amir0000-0003-3370-105X
Liao, Bolin0000-0002-0898-0803
Additional Information:This work was supported by NSF grant DMR-0964886 and Air Force Office of Scientific Research Grant FA9550-11-1-0055 in the Physical Biology Center for Ultrafast Science and Technology at California Institute of Technology, which is supported by the Gordon and Betty Moore Foundation.
Funding AgencyGrant Number
Air Force Office of Scientific Research (AFOSR)FA9550-11-1-0055
Gordon and Betty Moore FoundationUNSPECIFIED
Record Number:CaltechAUTHORS:20191111-085308090
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99770
Deposited By: Tony Diaz
Deposited On:12 Nov 2019 23:20
Last Modified:12 Nov 2019 23:20

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