Synthesis and Photoluminescence Properties of GaAs Nanowires Grown on Fused Quartz Substrates

GaAs nanowires are synthesized on fused quartz substrates by using molecular beam epitaxy via a vapor-liquidsolid mechanism with gold as the catalyst. High resolution-transmission electron microscopy is used to probe crystal quality and growth direction. Micro-photoluminescence measurements are carried out to examine the optical properties of GaAs NWs. The low-temperature photoluminescence (PL) emission of nanowires (NWs) has a peak at 1.513 eV, 2 meV lower than the zinc blende GaAs free exciton energy. The temperature-dependent band gap of NWs is seen to be somewhat different from that observed in bulk GaAs, and the PL rapidly quenches above 150 K, with an activation energy of 6.3 meV reflecting the presence of the longitudinal twins' structure.