  Quantum dots (QDs) based on III-nitride semiconductors are promising for
single photon emission at non-cryogenic temperatures due to their large exciton
binding energies. Here, we demonstrate GaN QD single photon emitters operating
at 300 K with $g^{(2)}(0) = 0.17 \pm 0.08$ under continuous wave excitation. At
this temperature, single photon emission rates up to $6\times10^6 \,
\text{s}^{-1}$ are reached while $g^{(2)}(0) \leq 0.5$ is maintained. Our
results are achieved for GaN QDs embedded in a planar AlN layer grown on
silicon, representing a promising pathway for future interlinkage with optical
waveguides and cavities. These samples allow exploring the limiting factors to
key performance metrics for single photon sources, such as brightness and
single photon purity. While high brightness is assured by large exciton binding
energies, the single photon purity is mainly affected by the spectral overlap
with the biexcitonic emission. Thus, the performance of a GaN QD as a single
photon emitter depends on the balance between the emission linewidth and the
biexciton binding energy. We identify small GaN QDs with an emission energy in
excess of 4.2 eV as promising candidates for future room temperature
applications, since the biexciton binding energy becomes comparable to the
average emission linewidth of around 55 meV.
