High compositional homogeneity in In-rich InGaAs nanowire arrays on nanoimprinted SiO 2/Si (111)
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We report improved homogeneity control of composition-tuned In Ga As (x 0.4) nanowire (NW) arrays grown by catalyst-free molecular beam epitaxy (MBE) on nanoimprinted SiO /Si (111) substrates. Using very high As/(GaIn) ratios at growth temperatures of 550 °C enabled uniform incorporation of the respective group-III elements (In,Ga) over the investigated composition range, confirmed by high-resolution x-ray diffraction (HRXRD) and energy dispersive x-ray spectroscopy. Low-temperature (20 K) photoluminescence of these In-rich In Ga As NW ensembles reveal state-of-the-art linewidths of ∼29-33 meV. These are independent of Ga content, suggesting an overall low degree of phase separation. In contrast, self-assembled, non-periodic In Ga As NW arrays show larger inhomogeneity with increased peakwidths in 2θ-ω HRXRD scans as well as broadened Raman modes. These results demonstrate the excellent potential of site-selective MBE growth of high-periodicity non-tapered In Ga As NW arrays with low size and composition dispersion for optimized device integration on Si. © 2012 American Institute of Physics.