Control of GaAs nanowire morphology and crystal structure

Abstract

The morphology and crystal structure of Au-seeded GaAs nanowires (NWs) grownby molecular beam epitaxy were investigated as a function of the temperature,V/III flux ratio, and Ga flux. Low and intermediate growth temperatures of 400 and500 °C resulted in a strongly tapered morphology, with stacking faults occurring at an average rate of0.1 nm−1. NWs with uniform diameter and the occurrence of crystal defectsreduced by more than an order of magnitude were achieved at600 °C,a V/III flux ratio of 2.3, and a Ga impingement rate on the surface of0.07 nm s−1. Comparison of nanowire densities on the various post-growth surfaces suggests a possibleincubation time between the moment the Ga shutter is opened and when nanowire growthis initiated. Increasing the flux ratio favored uniform sidewall growth, making the processsuitable for the fabrication of core–shell structures.