Metamorphic GaAs/GaAsBi Heterostructured Nanowires.
GaAs/GaAsBi coaxial multishell nanowires were grown by molecular beam epitaxy. Introducing Bi results in a characteristic nanowire surface morphology with strong roughening. Elemental mappings clearly show the formation of the GaAsBi shell with inhomogeneous Bi distributions within the layer surrounded by the outermost GaAs, having a strong structural disorder at the wire surface. The nanowire exhibits a predominantly ZB structure from the bottom to the middle part. The polytipic WZ structure creates denser twin defects in the upper part than in the bottom and middle parts of the nanowire. We observe room temperature cathodoluminescence from the GaAsBi nanowires with a broad spectral line shape between 1.1 and 1.5 eV, accompanied by multiple peaks. A distinct energy peak at 1.24 eV agrees well with the energy of the reduced GaAsBi alloy band gap by the introduction of 2% Bi. The existence of localized states energetically and spatially dispersed throughout the NW are indicated from the low temperature cathodoluminescence spectra and images, resulting in the observed luminescence spectra characterized by large line widths at low temperatures as well as by the appearance of multiple peaks at high temperatures and for high excitation powers.
Graduate School of Science and Engineering, Ehime University , 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan.
Fumitaro
F
Ishikawa
Graduate School of Science and Engineering, Ehime University , 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan.
Yoshihiko
Y
Akamatsu
WPI Center for Materials Nanoarchitectonics, National Institute for Materials Science , 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
Kentaro
K
Watanabe
Transmission Electron Microscopy Station, National Institute for Materials Science , 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan.
Fumihiko
F
Uesugi
SM Business Unit, JEOL Ltd. , 3-1-2 Musashino, Akishima, Tokyo 196-8558, Japan.
Shunsuke
S
Asahina
Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany.
Uwe
U
Jahn
Graduate School of Science and Engineering, Ehime University , 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan.
Satoshi
S
Shimomura
GaAs; GaAsBi; Semiconductor nanowires; luminescence; roughening