title: Observation of Strong Reflection of Electron Waves Exiting a Ballistic Channel at Low Energy.
abstract: Wave scattering by a potential step is a ubiquitous concept. Thus, it is surprising that theoretical treatments of ballistic transport in nanoscale devices, from quantum point contacts to ballistic transistors, assume no reflection even when the potential step is encountered upon exiting the device. Experiments so far seem to support this even if it is not clear why. Here we report clear evidence of coherent reflection when electron wave exits the channel of a nanoscale transistor and when the electron energy is low. The observed behavior is well described by a simple rectangular potential barrier model which the Schrodinger's equation can be solved exactly. We can explain why reflection is not observed in most situations but cannot be ignored in some important situations. Our experiment also represents a direct measurement of electron injection velocity - a critical quantity in nanoscale transistors that is widely considered not measurable.
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899-8120, USA.
authors.forename: Canute I
authors.initials: CI
authors.lastname: Vaz
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899-8120, USA; Institute of Microelectronics, Peking University, Beijing 100871, China.
authors.forename: Changze
authors.initials: C
authors.lastname: Liu
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899-8120, USA.
authors.forename: Jason P
authors.initials: JP
authors.lastname: Campbell
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899-8120, USA.
authors.forename: Jason T
authors.initials: JT
authors.lastname: Ryan
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899-8120, USA; IBM Research, Albany, NY 12205, USA.
authors.forename: Richard G
authors.initials: RG
authors.lastname: Southwick
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899-8120, USA.
authors.forename: David
authors.initials: D
authors.lastname: Gundlach
authors.affiliation: Taiwan Semiconductor Manufacturing Corporation, Hsinchu 30844, Taiwan.
authors.forename: Anthony S
authors.initials: AS
authors.lastname: Oates
authors.affiliation: Institute of Microelectronics, Peking University, Beijing 100871, China.
authors.forename: Ru
authors.initials: R
authors.lastname: Huang
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899-8120, USA.
authors.forename: Kin P
authors.initials: KP
authors.lastname: Cheung