Effect of V/III ratio on the structural and optical properties of self-catalysed GaAs nanowires.

The performance of GaAs nanowire (NW) devices depends critically on the presence of crystallographic defects in the NWs such as twinning planes and stacking faults, and considerable effort has been devoted to understanding and preventing the occurrence of these. For self-catalysed GaAs NWs grown by molecular beam epitaxy (MBE) in particular, there are in addition other types of defects that may be just as important for NW-based optoelectronic devices. These are the point defects such as the As vacancy and the Ga antisite occurring due to the inherently Ga-rich conditions of the self-catalysed growth. Here we demonstrate experimentally the effects of these point defects on the optical properties of GaAs/AlGaAs core-shell NWs grown by self-catalysed MBE. The present results enable insight into the role of the point defects both on their own and in conjunction with crystallographic planar defects.