  Single-photon sources are essential building blocks in quantum photonic
networks, where quantum-mechanical properties of photons are utilised to
achieve quantum technologies such as quantum cryptography and quantum
computing. Most conventional solid-state single-photon sources are based on
single emitters such as self-assembled quantum dots, which are created at
random locations and require spectral filtering. These issues hinder the
integration of a single-photon source into a scaleable photonic quantum network
for applications such as on-chip photonic quantum processors. In this work,
using only regular lithography techniques on a conventional GaAs quantum well,
we realise an electrically triggered single-photon source with a GHz repetition
rate and without the need for spectral filtering. In this device, a single
electron is carried in the potential minimum of a surface acoustic wave (SAW)
and is transported to a region of holes to form an exciton. The exciton then
decays and creates a single photon in a lifetime of ~ 100ps. This SAW-driven
electroluminescence (EL) yields photon antibunching with $g^{(2)}(0) = 0.39 \pm
0.05$, which satisfies the common criterion for a single-photon source
$g^{(2)}(0) < 0.5$. Furthermore, we estimate that if a photon detector receives
a SAW-driven EL signal within one SAW period, this signal has a 79%-90% chance
of being a single photon. This work shows that a single-photon source can be
made by combining single-electron transport and a lateral n-i-p junction. This
approach makes it possible to create multiple synchronised single-photon
sources at chosen positions with photon energy determined by quantum-well
thickness. Compared with conventional quantum-dot-based single-photon sources,
this device may be more suitable for an on-chip integrated photonic quantum
network.
