Shell to core carrier-transfer in MBE-grown GaAs/AlGaAs core-shell nanowires on Si(100) substrates

We report on the shell-to-core carrier-transfer in GaAs/Al0.1Ga0.9As core-shell nanowires grown on Si(1 0 0) substrates via molecular beam epitaxy. The nanowires are dominantly zincblende and are tilted with respect to the substrate surface. Photoluminescence (PL) excitation spectrosocopy at 77 K revealed an abrupt increase in the GaAs PL intensity at excitation above the Al0.1Ga0.9As shell bandgap which is attributed to shell to core carrier-transfer. More carriers from the Al0.1Ga0.9As transfer to the GaAs at T > 90 K, as observed in the time-resolved PL and temperature dependence of the relative PL intensities of GaAs and Al0.1Ga0.9As due to the ionization of the traps within the Al0.1Ga0.9As. Using a coupled rate equation model that takes into account shell to core carrier-transfer, the average recombination time constants of Al0.1Ga0.9As shell tau(rec,s) = 400 ps (580 ps) and GaAs core tau(rec,c) = 600 Ps (970 ps) were obtained from the time-resolved PL at 300 K (77 K). Carrier-transfer time constants tau(CT) = 50 Ps (55 ps) at 300 K (77 K) were also obtained. (C) 2014 Elsevier B.V. All rights reserved.