Carrier capture into InAs/GaAs quantum dots detected by a simple degenerate pump–probe technique

We demonstrate that the carrier capture and relaxation processes in InAs/GaAs quantum dots can be detected by a simple degenerate pump–probe technique. We have observed a rising process in the transient reflectivity, following the initial fast relaxation in a GaAs matrix, and assigned this rising process to the carrier capture from the GaAs barriers to the InAs layers. The assignment was modeled using the Kramers–Kronig relations. The capture time was found to depend strongly on the InAs layer thickness as well as on the excitation density and photon energy.