Observation of Phonon Bottleneck in Quantum Dot Electronic Relaxation

Time-resolved differential transmission measurements of self-assembled ${\mathrm{In}}_{0.4}{\mathrm{Ga}}_{0.6}\mathrm{As}$ quantum dots clearly indicate a phonon bottleneck between the $n=2\mathrm{}$ and $n=1\mathrm{}$ electronic levels. The key to this observation is the generation of electrons in dots where there are no holes so that electron-hole scattering does not mask the bottleneck. We use a simple carrier capture model consisting of two capture configurations to explain the bottleneck signal and offer arguments to rule out other possible sources of the signal.