Structural and chemical evolution of the spontaneous core-shell structures of AlxGa1-xN/GaN nanowires.
A study by electron microscopy techniques of the structural and compositional properties of Al x Ga1-x N/GaN nanowire (NW) heterostructures on Si(111) is presented. Al x Ga1-x N depositions grown without catalyst by plasma-assisted molecular beam epitaxy were designed to form NWs in the range of 0.20<x<0.40 with different lengths and growth temperatures. The NWs exhibit a well-defined core-shell radial structure with a complex chemical distribution along and across the growth direction that finally affects the NW morphology. All the wires have an initial stage with a maximum Al content in the core slightly above the GaN/Al x Ga1-x N interface, which initially decreases exponentially with the NW height depending on the nominal Al content and the growth temperature. In longer NWs, this trend changes and evolves increasing both the Al/Ga ratio and the core diameter as well as sharpening the shell. Adatom surface kinetic differences and the geometrical shadow effect during the growth are the probable drivers of this behavior.
Dpto. Ciencia de los Materiales e Ingeniería Metalúrgica y Q.I.,Facultad de Ciencias,Apdo. 40,11510 Puerto Real,Cádiz,Spain.
Rabie
R
Fath Allah
Dpto. Ciencia de los Materiales e Ingeniería Metalúrgica y Q.I.,Facultad de Ciencias,Apdo. 40,11510 Puerto Real,Cádiz,Spain.
Teresa
T
Ben
Dpto. Ciencia de los Materiales e Ingeniería Metalúrgica y Q.I.,Facultad de Ciencias,Apdo. 40,11510 Puerto Real,Cádiz,Spain.
David
D
González