Electron escape rate from coupled multiple quantum wells: Effects of coherence length and hopping

Electron escape rates from coupled quantum wells with a small number of periods have been determined by measuring the photoluminescence decay time. In the absence of an electric field, the escape time depends strongly on the coherence length of the wave function which is estimated to extend over six well layers. The escape time of electrons localized by an electric field reflects the hopping probability which is affected by the wave-function overlap between adjacent well layers. This probability is enhanced when LO-phonon-assisted hopping is possible.