title: Ultrafast field dynamics in large-aperture photoconductors.
abstract: We investigated field screening mechanisms in large-aperture GaAs photoconductors, using an ultrafast pump--probe terahertz technique. After photoexcitation the bias field decreases to an intensity-dependent value as a result of near-field screening of the bias field. For longer delays the field exhibits an intensity-dependent decrease that results from a space-charge field caused by transport-induced charge separation. These measurements support recent theoretical results that the dominant saturation mechanism that limits terahertz output from large-aperture photoconductors is near-field screening of the bias field because the space-charge field develops on a much longer time scale than that of the terahertz pulse.
authors.affiliation: Los Alamos National Laboratory, MS D429, Los Alamos, New Mexico 87545, USA.
authors.forename: A J
authors.initials: AJ
authors.lastname: Taylor
authors.forename: G
authors.initials: G
authors.lastname: Rodriguez
authors.forename: D
authors.initials: D
authors.lastname: Some