Manipulated growth of GaAs nanowires: Controllable crystal quality and growth orientations via a supersaturation-controlled engineering process

Controlling the crystal quality and growth orientation of high performance III-V compound semiconductor nanowires (NWs) in a large-scale synthesis is still challenging, which could restrict the implementation of nanowires for practical applications. Here we present a facile approach to control the crystal structure, defects, orientation, growth rate and density of GaAs NWs via a supersaturation-controlled engineering process by tailoring the chemical composition and dimension of starting Au_xGa_y catalysts. For the high Ga supersaturation (catalyst diameter < 40 nm), NWs can be manipulated to grow unidirectionally along 〈111〉 with the pure zinc blende phase with a high growth rate, density and minimal amount of defect concentration utilizing the low-melting-point catalytic alloys (AuGa, Au ₂Ga, and Au₇Ga₃ with Ga atomic concentration > 30%), whereas for the low Ga supersaturation (catalyst diameter > 40 nm), NWs are grown inevitably with a mixed crystal orientation and high concentration of defects from high-melting-point alloys (Au₇Ga ₂ with Ga atomic concentration < 30%). In addition to the complicated control of processing parameters, the ability to tune the composition of catalytic alloys by tailoring the starting Au film thickness demonstrates a versatile approach to control the crystal quality and orientation for the uniform NW growth.