Abstract

There are two mechanisms which determine the temporal behavior of photoconductive switching: (1) space-charge motion induced by the separation of electrons and holes which scrreens off the bias field; (2) THz radiation by accelerating carriers which acts to oppose the bias field (in fact ballistically accelerated electrons, which we have recently observed, are expected to radiate very efficiently.^[1] Thus, to probe the effect of carrier transport on field switching dynamics, we performed two experiments on an Al.₃Ga.₇As/GaAs multiple-quantum-well sample, with a parallel field applied across a 50-µm gap (using a horizontal p-i-n structure),^[1] using a 76-MHz 100-fs tunable Ti:Sapphire laser at 820 nm. We probed the internal field .of the gap via excitonic electro-absorption.^[2] Also we measured the radiation pulse from the same gap by standard THz photoconductive detection.^{[2, 3]}

© 1992 IQEC