Evolution of the Length and Radius of Catalyst-Free III-V Nanowires Grown by Selective Area Epitaxy.

We present a new model for the length and radius evolution of catalyst-free III-V nanowires grown by selective area epitaxy. We consider simultaneous axial and radial growth of nanowires, which is more typical for this technique compared to the vapor-liquid-solid growth of nanowires. Analytic expressions for the time evolution of the nanowire length and radius are derived, showing the following properties. As long as the nanowire length is shorter than the collection length of group III atoms on the sidewalls, the length evolves superlinearly and the radius evolves linearly with time. For longer nanowires, both the length and radius increase sublinearly with time. The scaling growth laws are controlled by a single parameter that depends on group V flux. The model fits well the data on the selective area growth of InAs and GaAs nanowires by different techniques. Overall, these results can be used for controlling the catalyst-free growth of III-V nanowires and their morphology, including ternary III-V material systems.