High compositional homogeneity in In-rich InGaAs nanowire arrays on nanoimprinted SiO_2/Si (111)

摘要

We report improved homogeneity control of composition-tuned In_(1-x)Ga_xAs (x<0.4) nanowire (NW) arrays grown by catalyst-free molecular beam epitaxy (MBE) on nanoimprinted SiO_2/Si (111) substrates. Using very high As/(Ga+In) ratios at growth temperatures of 550 ℃ enabled uniform incorporation of the respective group-Ill 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_(1-x)Ga_xAs 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_(1-x)Ga_xAs NW arrays show larger inhomogeneity with increased peakwidths in 26-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_(1-x)Ga_xAs NW arrays with low size and composition dispersion for optimized device integration on Si.