Aluminum-Induced Photoluminescence Red Shifts in Core-Shell GaAs/AlxGa1-xAs Nanowires
2013 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 13, no 8, 3581-3588 p.Article in journal (Refereed) Published
We report a new phenomenon related to Al-induced carrier confinement at the interface in core-shell GaAs/AlxGa1-xAs nanowires grown using metal-organic vapor phase epitaxy with Au as catalyst. All AlxGa1-xAs shells strongly passivated the GaAs nanowires, but surprisingly the peak photoluminescence (PL) position and the intensity from the core were found to be a strong function of Al composition in the shell at low temperatures. Large and systematic red shifts of up to similar to 66 nm and broadening in the PL emission from the GaAs core were observed when the Al composition in the shell exceeded 3%. On the contrary, the phenomenon was observed to be considerably weaker at the room temperature. Cross-sectional transmission electron microscopy reveals Al segregation in the shell along six Al-rich radial bands displaying a 3-fold symmetry. Time-resolved PL measurements suggest the presence of indirect electron-hole transitions at the interface at higher Al composition. We discuss all possibilities including a simple shell-core-shell model using simulations where the density of interface traps increases with the Al content, thus creating a strong local electron confinement. The carrier confinement at the interface is most likely related to Al inhomogeneity and/or Al-induced traps. Our results suggest that a low Al composition in the shell is desirable in order to achieve ideal passivation in GaAs nanowires.
Place, publisher, year, edition, pages
2013. Vol. 13, no 8, 3581-3588 p.
GaAs/AlGaAs, core-shell nanowires, MOVPE, MOCVD, Al segregation, TRPL
Atom and Molecular Physics and Optics Nano Technology
IdentifiersURN: urn:nbn:se:kth:diva-127413DOI: 10.1021/nl4012613ISI: 000323241000021ScopusID: 2-s2.0-84881584613OAI: oai:DiVA.org:kth-127413DiVA: diva2:644084
FunderSwedish Research CouncilEU, FP7, Seventh Framework Programme
QC 201309132013-08-292013-08-292013-09-13Bibliographically approved