GaAs nanowires have been grown by Ga-assisted chemical beam epitaxy (CBE) on Si(111) substrates using triethylgallium (TEGa) and tertiarybutylarsine (TBAs). In this work, we present a reproducible and reliable way to prepare Si(111) substrates allowing for the Ga droplet formation on top of the oxidized Si(111) surface, and enabling to the nucleation of GaAs nanowires by CBE through a Ga-assisted vapor-liquid-solid (VLS) mechanism. In addition, an alternative growth procedure has been developed to prevent the formation of GaAs surface structures, including traces and nanocrystals, which are the main responsible for limiting the maximum nanowire length because they act as a sink for atomic species. This procedure consists in a two-steps growth, inserting a self-aligned native SiOx layer after the first growth step, increasing the maximum nanowire length up to reaching values of 5 microns, and improving the nanowire aspect ratio. Resulting nanowires present a pure zinc blende structure free of rotational twins as determined by reflection high-energy electron diffraction (RHEED) and transmission electron microscopy (TEM). Dielectrophoresis (DEP) is presented here as a potential way to trap and to align GaAs nanowires, connecting a pair of conductive electrodes with a spacing below the nanowire length. In this regard, nanowires are transferred to a liquid medium by sonication forming a suspension of nanowires. A micro-droplet extracted from the nanowire suspension is drop-casted on a sample with pre-defined conductive electrodes while an alternating-current (AC) electric field is applied between them, leading to nanowire trapping at high electric field regions (positive DEP). The assembling efficiency has been analyzed as a function of the DEP parameters, involving amplitude and frequency of the AC signal, relative orientation of the nanowire with respect to the electric field, etc. DEP conditions were optimized, allowing for the fabrication of a single GaAs nanowire based electronic devices. Photoresponse of these nanowires was analyzed in depth, observing high sensitivity to the visible illumination even for the microscope lamp intensity, and showing near two orders of magnitude higher current when comparing to the dark current level.
|Publication status||Published - 4 Oct 2015|
|Event||31st North American Molecular Beam Epitaxy Conference - Mayan Riviera, Mexico|
Duration: 4 Oct 2015 → 7 Oct 2015
|Conference||31st North American Molecular Beam Epitaxy Conference|
|Period||4/10/15 → 7/10/15|