Intrinsic limits governing MBE growth of Ga-assisted GaAs nanowires on Si(111)

TL;DR

This paper investigates the intrinsic physical limits of Ga-assisted GaAs nanowire growth on Si(111), focusing on diffusion and desorption regimes, and identifies optimal conditions for maximum growth rate and uniformity.

Contribution

It reveals the diffusion-enhanced and desorption-limited growth regimes and quantifies the maximum axial growth rate under dynamical equilibrium conditions.

Findings

Growth regimes depend on temperature and flux conditions.

Maximum growth rate occurs at dynamical equilibrium in Ga droplets.

Diameter influences axial growth rate through diffusion effects.

Abstract

Diffusion-enhanced and desorption-limited growth regimes of Ga-assisted GaAs nanowires were identified. In the latter regime, the number of vertical NWs with a narrow length distribution was increased by raising the growth temperature. The maximum axial growth rate; which can be quantified by the supplied rate of As atoms, is achieved when a dynamical equilibrium state is maintained in Ga droplets i.e. the number of impinging As atoms on the droplet surface is equivalent to that of direct deposited Ga atoms combining with the diffusing ones. The contribution of Ga diffusion to the wire growth was evidenced by the diameter-dependent NW axial growth rate.