Growth of one-dimensional III–V structures on Si nanowires and pre-treated planar Si surfaces

This paper presents a technique that allows the growth of epitaxial GaAs nanowires that are aligned to the crystal directions of the Si substrate. Low-pressure chemical vapor deposition (LP-CVD) grown Si nanowires were used as templates for molecular beam epitaxy (MBE) growth. The growth direction of the nanowires aligns with the [1 1 1] direction perpendicular to the Si substrate. After deposition of 200 nm GaAs in a solid source MBE system, we observed the formation of GaAs whiskers perpendicular to the {1 1 2} sidewalls of Si nanowires. By TEM analysis, the crystal structure of the GaAs nanostructures could be identified as wurtzite, where the growth axis of the wires was in the [0 0 0 1] direction. The whiskers are of good crystalline quality as no dislocations or stacking faults were observed in large areas by TEM, which makes these structures potential candidates for III–V integration on Si. In parallel to these experiments, we found a growth technique that allows GaAs nanowires to grow along the [1 1 1] direction of the planar Si [1 1 2] substrates. III–V nanowires with comparable geometry but higher density could be realized.