Figure 1

Photoluminescence images for our single QW sample taken at excitation powers of 50, 265, and $296\mu \mathrm{W}$, are shown in the left panel (a)–(c). The middle panel (d)–(f) shows the results of the model calculations. All images are $700\times 700\mu \mathrm{m}$. The right panel (g)–(i) presents the experimentally observed center spot (olive) and ring (purple) emission spectra. The sample was measured at $T=8\mathrm{K}$, and excited with a HeNe laser ($632\mathrm{nm}$) with a spot diameter of $\sim 60\mu \mathrm{m}$.Reuse & Permissions

Figure 2

Comparison between the experimental and model calculated excitation power dependences: (a) experimental and (e) calculated ring radius; (b) the measured linewidth and (c) the energy of the center spot luminescence (olive circles) and the ring luminescence (purple circles); (f) model calculated linewidth of the luminescence of the center spot and ring assuming degenerate 2D electron-hole plasma; (g) model calculated energies of the center spot and ring luminescence based on band gap renormalization; (d) experimental and (h) calculated PL peak intensity at the center spot and the ring. Vertical dashed lines mark the onset of the ring formation.Reuse & Permissions

Figure 3

(a) The energy profile of the QW structure in the growth direction and the relevant electronic processes under photoexcitation (see text). (b) Schematic description of in-plane distributions of cold electrons (open red circles) and excess cold holes (open blue circles) under steady state. The excitation spot is marked by the shaded circular area. The recombination of electrons and holes at the boundary gives rise to the ring pattern. (c) Calculated cold electron (red) and hole (blue) density profiles and the PL intensity (olive) profile for a CW excitation at a power of $350\mu \mathrm{W}$. The black dashed line shows the incident photon intensity radial profile. (d) is an expanded view of (c) around the ring position. (e) Calculated emission pattern cross section as a function of time after the excitation power is turned off. The ring PL and radius decay on a time scale of a microsecond. (f) An expanded view of (e) for very short times immediately after the power is turned off showing that the center spot PL decays on a time scale of picoseconds.Reuse & Permissions