Aluminum-Induced Photoluminescence Red Shifts in Core–Shell GaAs/Al x Ga 1– x As Nanowires
2013; American Chemical Society; Volume: 13; Issue: 8 Linguagem: Inglês
10.1021/nl4012613
ISSN1530-6992
AutoresVeer Dhaka, Jani Oksanen, Hua Jiang, Tuomas Haggrén, Antti I. Nykänen, Reza Sanatinia, Joona‐Pekko Kakko, Teppo Huhtio, Marco Mattila, Janne Ruokolainen, S. Anand, Esko I. Kauppinen, Harri Lipsanen,
Tópico(s)Semiconductor materials and devices
ResumoWe report a new phenomenon related to Al-induced carrier confinement at the interface in core-shell GaAs/Al(x)Ga(1-x)As nanowires grown using metal-organic vapor phase epitaxy with Au as catalyst. All Al(x)Ga(1-x)As 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 ~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.
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