Modeling the photoluminescence lifetime in realistic quantum wires

We present a theoretical model of the time-resolved excitonic photoluminescence in quantum wires. We study the role of disorder and of the exciton–free-carrier interaction on the temperature dependence of the photoluminescence lifetime. We find that at low temperature the exciton population is not thermalized in disordered quantum wires and that the lifetime is mainly determined by the localization length of the exciton. However, for large localization lengths or high enough temperatures the exciton population thermalizes within its lifetime and the temperature dependence becomes square-root-like. The inclusion of free carriers leads to an increase of the lifetime at high temperatures and to a quasiexponential temperature dependence.

Figure 1

Temperature dependence of the PL lifetime for different disorder parameters. (i) (crosses): $\sigma =0.1\text{meV}$, $\xi =18\text{nm}$. (ii) (open symbols): $\sigma =6\text{meV}$, $\xi =50\text{nm}$. (iii) (full symbols): $\sigma =4\text{meV}$, $\xi =18\text{nm}$. As a reference the continuous line represents a square-root dependence.

Figure 2

Population distribution for the three disorder configurations at $T=10\mathrm{K}$ and $2\text{ns}$ after laser excitation. Zero energy corresponds to the $k=0$ state in an ideal QWR.

Figure 3

Comparison between the temperature dependence of the excitonic PL lifetime taking into account (triangles) and ignoring (dots) free carriers ($\sigma =4\text{meV}$, $\xi =21\text{nm}$).