Alloying can be complex to understand because at least three different elements are involved Au, As, Ga. Therefore a ternary phase diagram must once again be studied in order to decide temperatures that would allow for eutectic stable liquid (eutectic point is the lowest melting point achieved by a mixture of metals) or solid alloys. \cite{Joyce_2011}

Vapor-liquid-solid-hydride vapor phase epitaxy (VLS-HVPE) is a technique that has allowed for the growth of exceptionally long (tens of micrometers) and defect free NW with a mean diameter of 50 nm. A gold monoloayer is placed on top of a GaAs substrate. The GaCl precursors allow for exceptionally fast decomposition and hence delivery of Ga for NW growth. In addition, the Cl species suppress radial growth of the NW. The assumption of fast Ga atom delivery to the liquid catalyst has been modeled by Andre and co-workers, resulting in good agreement with experiment.\cite{Andr__2014}

Although VLS and MOCVD are techniques that have been commonly used for decades there are still unknowns about the mechanism of growth mentioned earlier. \cite{Persson_2004} \cite{Dick_2005} In particular a solid phase diffusion mechanism in addition to the liquid phase mechanism for GaAs nanowire growth has been proposed. \cite{Persson_2004} An experiment growing two types of GaAs nanowires, differing only in method growth termination, was conducted. Method one included switching off the Ga pressure while maintaining As pressure, and method two involved switching off the gas supply of both at the same time. X-ray energy dispersive spectrometry reveal the ratio of Ga and As in the nanowire body and seed particle, and results conclude that the concentration of Ga for eutectic melt is never reached, suggesting a solid phase mechanism. \cite{Persson_2004}

Gas Source Molecular Beam Epitaxy (GS-MBE) coupled with Au particles has been successfully used to grow GaAs nanowires.\cite{Plante_2006}. Briefly, GS-MBE works as follows...Samples are carefully prepared so that a clean single crystal face is oriented towards the beam source. The beam source is then placed at a sufficient distance to allow uniform deposition onto the surface. The growth rates of the NW depend on the flux of gas used and formation rate of clusters.\cite{9780199544219} The mechanism of Nanowire growth reveals that the role of the Au catalyst is different than that described above for VLS and MOCVD. MBE GaAs nanowire growth was studied as a function of temperature, As:Ga ratio, Au seed particle size (20-800nm), revealing two main mechanism with different rates of nanowire formation.\cite{Plante_2006} For Au droplet catalyst below the diameter size of 105-130nm, the height of the wire is driven by the diffusion of Ga/As gas from the walls up to the tip of the wire. For catalyst with diameters greater than 103nm, bulk diffusion through the metal catalyst is responsible for nanowire growth.\cite{Plante_2006}

Bulk synthesis of GaAs include an “electrodeposition of gold particles” method. While Au catalyst have been used in evaporated, aerosol and colloid particle forms, these methods make it challenging to grow NW in a pattern, making the techniques less dependable for high redproducibility and consistency. Electrodeposition in conjunction with lithography has succesfully been used to produce nanoscale patterns.\cite{Jafari_Jam_2015} The method works as follows...nanoimprint lithography is used to define a pattern on a substrate with resist, resist residues are then removed by ion etching.Then electrodeposition (a process that uses electric current to reduce dissolved gold metal cations so that they form a coherent metal coating on the electrode’s exposed parts) occurs by placing the patterned substrate/resist wafer into a solution of gold. After the gold deposition, resist stripping is performed once more so that only the substrate and gold pattern are left.\cite{Jafari_Jam_2015} Advantages (compared to other methods such as thermal evaporation) include higher throughput, and reduced gold consumption by a factor of 300.