Nonclassical light emission, such as entangled and single-photon
emission, has attracted significant interest because of its importance
in future quantum technology applications. In this work, we study
the potential of wurtzite (In,Ga)N/GaN quantum dots for novel nonclassical
light emission, namely, twin-photon emission. Our calculations, based
on a fully atomistic many-body framework, reveal that the combination
of carrier localization due to random alloy fluctuations in the dot,
spin–orbit coupling effects, underlying wurtzite crystal structure,
and built-in electric fields leads to an excitonic fine structure
that is very different from that of more “conventional”
zinc-blende (In,Ga)As dots, which have been used so far for twin photon
emission. We show and discuss here that the four energetically lowest
exciton states are all bright and emit linearly polarized light. Furthermore,
three of these excitonic states are basically degenerate. All of these
results are independent of the alloy microstructure. Also, our calculations
reveal large exciton binding energies (>35 meV), which exceed the
thermal energy at room temperature. Therefore, (In,Ga)N/GaN dots are
very promising candidates for achieving efficient twin photon emission,
potentially at high temperatures and over a wide emission wavelength
range.