title: Imaging ultrafast carrier transport in nanoscale field-effect transistors.
abstract: In the present study, we visualize ultrafast carrier dynamics in one-dimensional nanoscale devices, such as Si nanowire and carbon nanotube transistors using femtosecond photocurrent microscopy. We investigate transit times of ultrashort carriers that are generated near one metallic electrode and subsequently transported toward the opposite electrode based on drift and diffusion motions. Conversely, pure diffusion motion is observed when the pump pulse is located in the middle of the nanowires. Carrier dynamics have been addressed for various working conditions, in which we found that the carrier velocity and pulse width can be manipulated by the external electrodes. In particular, the carrier velocities extracted from transit times increase for a larger negative gate bias because of the increased field strength at the Schottky barrier.
authors.affiliation: Department of Physics and Department of Energy Systems Research, Ajou University , Suwon 443-749, Korea.
authors.forename: Byung Hee
authors.initials: BH
authors.lastname: Son
authors.forename: Jae-Ku
authors.initials: JK
authors.lastname: Park
authors.forename: Jung Taek
authors.initials: JT
authors.lastname: Hong
authors.forename: Ji-Yong
authors.initials: JY
authors.lastname: Park
authors.forename: Soonil
authors.initials: S
authors.lastname: Lee
authors.forename: Yeong Hwan
authors.initials: YH
authors.lastname: Ahn
keywords: carbon nanotube; carrier transport; diffusion motion; femtosecond; field-effect transistor; nanowire