Influence of quasi-bound states on the carrier capture into quantum dots

An important characteristic of quantum dot (QD) materials is the timescale on which carriers are captured into the dots and relax to their ground state. The properties of devices based on QDs, such as lasers, thus rely on efficient carrier feeding to the active QD states. These processes are believed to be mediated by carrier-phonon and carrier-carrier interaction (Auger processes).

In systems of higher dimensionality, carrier relaxation via emission of LO (Longitudinal Optical) phonons is dominant. However, due to the discrete QD density of states, this process is often considered impossible unless the energy level separation equals the LO phonon energy, leading to a so-called phonon bottleneck.

This argument is based on the assumption that the carrier-LO phonon interaction is weak. It was shown that carriers in discrete QD states couple strongly to phonons and that the intersubband transition cannot be treated with Fermi's golden rule. Here, we extend the analysis to the coupling between carriers in quasi-bound continuum states and discrete QD states.