5 Absorption
and PL were acquired with a continuous-wave laser source
(HeCd, 325 nm) on individual wires cast onto a clean silicon
substrate. Low-temperature PL reveals a blue shift of 90 meV
in the band-edge emission from room temperature to 5 K
(Figure 4B). At 5 K, a well-resolved donor-bound exciton
peak at 368.87 nm (3.361 eV) and corresponding first-,
second-, and third-order phonon replicas at 379.56 nm (3.266
eV), 389.23 nm (3.185 eV), and 397.04 nm (3.123 eV) are
visible. The shoulder at 364.1 nm (3.404 eV) is attributed
to the free exciton transition. The peak centered at 372.8
nm (3.326 eV) is assigned to a two-electron (2e) transition
that has been shown to emerge with donor-bound excitons