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SEM micrograph of GaN nanocolumns. The columns are long and 100 nm in width. The inset shows a high resolution TEM image of the end of a single column.
PL spectra from a nanocolumn at various excitation powers. The Stark shift of the peak at 3.333 eV, attributed to emission from InGaN quantum disks, is clearly visible. The inset shows the peak energy at various excitation powers.
The quantum disk lifetime as a function of excitation power. The decrease in lifetime saturates at a power density of , in alignment with the saturation of the Stark shift. The inset shows the decay at an excitation power density of .
Time evolution, at an excitation power density of , of the PL spectra presented in Fig. 2. The inset shows the first 700 ps of the evolution of the peaks at 355 nm and 370 nm . The transfer of carriers from the GaN column to the InGaN disk is inferred from the rise time of the InGaN peak.
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