Growth mechanisms for GaAs nanowires grown in CBE

We have investigated the growth of GaAs nanowires as a function of temperatures and source pressures on (I 1 1) B-oriented substrates in chemical beam epitaxy (CBE), to establish the mechanisms that govern wire growth and to optimize growth conditions. The grown nanowires were characterized with a scanning electron microscope (SEM). We found two mechanisms to be of importance for wire growth: (i) sufficiently long diffusion length of the group-III material on the 2D substrate surface and on the side facets of the nanowire to obtain rod-shaped nanowires and (ii) growth conditions that suppress growth rate on adjacent surfaces to enhance the wire growth. Favorable conditions for these mechanisms are growth temperatures between 515 and 535 degreesC, and As-rich growth conditions. Furthermore, we suggest that the growth mechanism of nanowires in CBE is based on surface-selective-growth (SSG) with a solid seed particle rather than conventional vapor-liquid-solid (VLS) growth. (C) 2004 Elsevier B.V. All rights reserved