Intersubband relaxation dynamics in semiconductor quantum structures

We monitor the temporal evolution of the electron population in the first and second subband of an undoped GaAs/AlGaAs asymmetric double quantum well after interband optical excitation by using an interband pump/intersubband probe technique. The spacing between the two subbands is smaller than the longitudinal optical phonon energy. We extract an intersubband lifetime of View the MathML source and a recombination time of View the MathML source at an excitation density of View the MathML source. Results from a simple rate equation model fit very well to our data.