Spatially controlled VLS epitaxy of gallium arsenide nanowires on gallium nitride layers

Abstract

We present Au catalyzed p-GaAs nanowire growth on n-GaN layers as a possible method to grow an arsenide on a nitride compound semiconductor by metal organic vapor phase epitaxy. The GaAs growth position, the nanowire density and the nanowire growth direction are controlled by a combination of vapor–liquid–solid growth and selective area epitaxy. Thus, a spatially controlled nanowire growth is attained, which is mandatory for device fabrication. The growth position is defined by lithographically positioned Au discs on n-GaN. By adapting the growth conditions (Q_TBAs, presaturation) the nanowire density is optimized. Lateral and vertical anisotropic nanowire growth is attained through VLS growth in structured SiO_x openings. Critical technological parameters for successful control of the growth direction are the positioning of the Au catalyst in relation to the SiO_x mask, the size of the eutectic in relation to the opening dimensions, and the SiO_x thickness. These results lead to distinct pn-junction positions and adjustable nanowire growth dimensions and directions.