Homogeneous broadening in quantum dots due to Auger scattering with wetting layer carriers

The homogeneous broadening in semiconductor quantum dot (QD) lasers and optical amplifiers is studied theoretically. Based on a model for the electronic states of the coupled QD–wetting layer (WL) system, Coulomb interaction matrix elements are calculated, including both screening and exchange interaction. The homogeneous broadening due to various Auger processes, involving scattering of carriers between WL states and confined QD states, is calculated. The effects of the orthogonalization of WL states, QD confinement, QD density, and carrier density on the homogeneous broadening are studied systematically. We found that such WL-assisted Auger scattering is very efficient with subpicosecond dephasing times, and it is the dominant channel for the homogeneous broadening at high carrier density. Good agreement is achieved when comparing our theoretical results and recent experimental data.

Figure 1

$T_{\mathit{I}}$, $T_{\mathit{II}}$, and $T_{\mathit{III}}$ in-scattering from initial states in filled circles to final states in open circles (and inverse for out-scattering).

Figure 2

(Color online) The broadening due to the $T_{\mathit{II}}$ and $T_{\mathit{III}}$ scattering versus carrier density, with various contributions plotted separately.

Figure 3

(Color online) The broadening versus carrier density including different numbers of confined hole levels.

Figure 4

(Color online) The contribution from the different carrier combinations versus carrier density.

Figure 5

(Color online) Broadening versus confinement strength, $\hslash {\omega }_{\mathit{tot}}$, for different hole effective masses.

Figure 6

(Color online) Broadening for different dot densities (a) versus carrier density and (b) versus carrier density divided by transparency carrier density, $n_{\mathit{tr}}$, using plane waves (PW) and orthogonalized plane waves (OPW). For the dot densities 1, 5, and $10\times {10}^{10}{\mathrm{cm}}^{-2}$ $n_{\mathit{tr}}=9.1\times {10}^{10}{\mathrm{cm}}^{-2}$, $2.0\times {10}^{11}{\mathrm{cm}}^{-2}$, and $3.3\times {10}^{11}{\mathrm{cm}}^{-2}$, respectively.

Figure 7

Comparison of experimental data of the homogeneous broadening by Borri et al. (Ref. 7) (squares) with the offset at $I=0$ removed (circles) and our calculated values using quasistatic plasmon-pole approximation (solid line) and static screening (dashed line) at different temperatures.