Au-Catalyst Assisted MOVPE Growth of CdTe Nanowires for Photovoltaic Applications

Vertically-aligned CdTe nanowire (NWs) were grown for the first time by metalorganic vapor phase epitaxy, using diisopropyl-telluride and dimethylcadmium as precursors, and Au nanoparticles as metal catalysts. The NWs were grown between 485 and 515 degrees C on (111) B-GaAs substrates, the latter overgrown with a 2-lm thick CdTe epilayer. To favor the Au-catalyst assisted process against planar deposition of CdTe, an alternate precursors flow process was adopted during NW self-assembly. Field emission electron microscopy observations and X-ray energy dispersive analyses of CdTe NWs revealed the presence of Au-rich droplets at their tips, the contact-angle between Au-droplets and NWs being similar to 130 degrees. The NW height increases exponentially with the growth temperature, indicating that the Au-catalyzed process is kinetics-limited (activation energy: similar to 57 kcal/mol), but no tapering is observed. Low temperature cathodoluminescence spectra recorded from single NWs evidenced a band-edge emission typical of zincblend CdTe, and a dominant (defects-related) emission band at 1.539 eV.