Control of fine-structure splitting and biexciton binding in ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ quantum dots by annealing

The distribution of the fine-structure splitting $ħ{\delta }_1$ and of the biexciton binding energy $ħ{\delta }_B$ are measured in a series of annealed InAs quantum dots. We find a decrease of $ħ{\delta }_1$ from $96\mu \mathrm{eV}$ to $6\mu \mathrm{eV}$ with increasing annealing temperature, indicating a symmetrizing of the in-plane confinement potential. The biexciton binding energy shows only a weak dependence on the confinement energy, which we attribute to a compensation between decreasing confinement and decreasing separation of electron and hole.