Growth and Characterization of MnAs Nanoclusters Embedded in GaAs Nanowires by Metal--Organic Vapor Phase Epitaxy

The authors report on the fabrication of MnAs/GaAs hybrid nanowires by combining selective-area metal-organic vapor phase epitaxy of GaAs nanowires and "endotaxy" of MnAs nanoclusters. MnAs nanoclusters are embedded in the six ridges of hexagonal GaAs nanowires as a result of endotaxy. From the cross-sectional characterizations by transmission electron microscopy, the average width of MnAs nanoclusters with the hexagonal NiAs-type crystal structure and the average depth in GaAs nanowires are estimated to be about 10 and 8 nm, respectively. The magnetic responses detected from the reference samples grown on planar GaAs (111) B layers show that ferromagnetic MnAs nanoclusters are formed. The diameter of nanoclusters grown in GaAs nanowires increases with decreasing growth temperature and/or increasing distance between the GaAs nanowires, while the density of nanoclusters increases with increasing growth temperature. It is found that the diameter and density of nanoclusters are strongly influenced by the gas supplied during the decrease in temperature after the nanocluster growth. (C) 2012 The Japan Society of Applied Physics