Dephasing processes in InGaAs quantum dots

摘要

We present temperature-dependent measurements of the dephasing time of the excitonic ground-state transition in strongly-confined InGaAs quantum dots, using a sensitive four-wave mixing heterodyne technique. At low temperature we measure a dephasing time of several hundred picoseconds. Between 7K and 100K the polarization decay consists of two distinct components, resulting in a non-Lorentzian lineshape with a narrow zero-phonon line and a broad band from excitpn-acoustic phonon interaction. We also explore the dephasing time beyond the one-exciton occupation by electrically injecting carriers. Electrical injection into the barrier region results in a dominantly pure dephasing of the excitonic ground-state transition and of the biexciton-to-exciton transition. Additionally, the temperature dependent dephasing of the biexciton-to-exciton transition indicates a correlated phonon scattering of the exciton and biexciton.