Experimental determination of adatom diffusion lengths for growth of InAs nanowires

Au-assisted InAs nanowires are grown using molecular beam epitaxy. By tailoring the growth and position of InAs nanowires, experimental values for the effective diffusion lengths of adatoms on both the substrate and nanowire sidewalls have been deduced. In the framework of a mass continuity growth model for group III elements, based on a simple kinetic but informative treatment without use of thermodynamic parameters, both shadowing effects and shared substrate diffusion areas are included. The growth model is fitted to two types of data, one for nanowires positioned in a quadratic array with varying pitch, and one for nanowires with axial heterostructures. For the given growth conditions the effective diffusion length for In adatoms on InAs NW sidewalls with wurtzite crystal structure is found to be 3μm, whereas the effective diffusion of Ga adatoms is an order of magnitude smaller. The minimum pitch to ensure independent growth, without influence from nearby NWs, is found to be around 2μm.

► An experimental method for determining effective diffusion lengths is presented.
► InAs nanowires are grown in arrays and with axial heterostructures.
► In adatoms are found to have an effective diffusion length of 3μm on sidewalls.
► Incorporation coefficients are included in a mass transport growth model.