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HRSEM images of nanowires grown on and substrates. Crystallographic structural studies using GIXRD show wurtzite GaN phase grown on both the substrates.
UV Raman spectra showing higher order modes for GaN nanowires grown on and substrates. Insets show slow scan upto third order modes for samples grown on both the substrates. A clear fourth order mode is recorded for sample grown on . Fitted PL peak at corresponding to direct band gap is also shown in the inset.
PL spectra of the epi-GaN and NWs with average diameter . epi-GaN shows a minor YL band along with a sharp direct band peak. A relatively broad direct band peak is shown for NWs with the absence of YL band. Inset shows multiphonon properties of these samples. Large backgrounds indicate strong PL signal in the samples.
Size dependent plot for calculated (continuous line) Frank-Condon interaction energy as well as experimentally observed values (scattered points with error bar) for GaN nanostructures. Calculated value for bulk GaN and experimental data for epi-GaN is also marked in the figure. Inset shows HRSEM images of NWs with average diameter and .
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