Excitation-induced dephasing in semiconductor quantum dots

A quantum kinetic theory is used to compute excitation induced dephasing in semiconductor quantum dots due to the Coulomb interaction with a continuum of states, such as a quantum well or a wetting layer. It is shown that a frequency dependent broadening together with nonlinear resonance shifts are needed for a microscopic explanation of the excitation induced dephasing in such a system, and that excitation induced dephasing for a quantum-dot excitonic resonance is different from quantum-well and bulk excitons.

Figure 1

Room-temperature absorption spectra for the combined quantum-dot/quantum-well system for carrier densities $2–4\times {10}^{11}{\mathrm{cm}}^{-2}$ in intervals of $5\times {10}^{10}{\mathrm{cm}}^{-2}$ (top to bottom, the base line of the spectra is shifted). The energy unit is the three-dimensional exciton binding energy ${ϵ}_R$, and the zero is at the zero-density quantum-dot excitonic transition $\hslash {\omega }_0$ including the electron-hole binding energy.

Figure 2

Absorption spectrum around quantum-dot resonance for carrier density $2.5\times {10}^{11}{\mathrm{cm}}^{-2}$ calculated using the full non-Markovian scattering contributions (solid curve), and the Markov approximation (dashed curve). The dotted curve is obtained from a least-squares fit with a Lorentzian.

Figure 3

${\Gamma }_{00}\left(\omega \right)=\mathrm{Re}{\Lambda }_{00}\left(\omega \right)$ [Eq. (3)] for three different carrier densities. The respective renormalized quantum-dot resonance is marked by a dot.

Figure 4

Excitation dependent broadening of the quantum-dot and quantum-well resonance lines calculated using the full non-Markovian scattering contributions (solid lines) and the Markov approximation (dashed line). Inset: Comparison to excitation induced broadening of the quantum-well excitonic resonance. The energy unit is the 3D exciton binding energy.