  Semiconductor quantum dots are converging towards the demanding requirements
of photonic quantum technologies. Among different systems, quantum dots with
dimensions exceeding the free-exciton Bohr radius are appealing because of
their high oscillator strengths. While this property has received much
attention in the context of cavity quantum electrodynamics, little is known
about the degree of indistinguishability of single photons consecutively
emitted by such dots and on the proper excitation schemes to achieve high
indistinguishability. A prominent example is represented by GaAs quantum dots
obtained by local droplet etching, which recently outperformed other systems as
triggered sources of entangled photon pairs. On these dots, we compare
different single-photon excitation mechanisms, and we find (i) a "phonon
bottleneck" and poor indistinguishability for conventional excitation via
excited states and (ii) photon indistinguishablilities above 90% for both
strictly resonant and for incoherent acoustic- and optical-phonon-assisted
excitation. Among the excitation schemes, optical phonon-assisted excitation
enables straightforward laser rejection without a compromise on the source
brightness together with a high photon indistinguishability.
