Control of GaAs nanowire morphology and crystal structure

The morphology and crystal structure of Au-seeded GaAs nanowires (NWs) grown by 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 and 500 °C resulted in a strongly tapered morphology, with stacking faults occurring at an average rate of 0.1 nm(-1). NWs with uniform diameter and the occurrence of crystal defects reduced by more than an order of magnitude were achieved at 600 °C, a V/III flux ratio of 2.3, and a Ga impingement rate on the surface of 0.07 nm s(-1). Comparison of nanowire densities on the various post-growth surfaces suggests a possible incubation time between the moment the Ga shutter is opened and when nanowire growth is initiated. Increasing the flux ratio favored uniform sidewall growth, making the process suitable for the fabrication of core-shell structures.