Photoluminescence evolution in GaAs/AlGaAs core/shell nanowires grown by MOCVD: Effects of core growth temperature and substrate orientation

• GaAs/AlGaAs core/shell nanowires (NW) are grown by metal-organic chemical-vapor deposition (MOCVD) on (1 0 0) and (1 1 1)B GaAs substrates.
• Dependence of optical characteristics on growth temperature and substrate orientation are investigated.
• At low core growth temperatures (below 450 °C), nanowires grown on (1 1 1)B substrates incorporate higher density of defects than wires on (1 0 0).
• Rising defect luminescence is observed in the PL spectra at temperatures higher than 450 °C and is concomitant with the increased epitaxial growth on the nanowire sidewalls.

We explore the growth temperature dependence of GaAs/AlGaAs core/shell nanowires (NW) grown by metal–organic chemical-vapor deposition (MOCVD) on (1 0 0) and (1 1 1)B GaAs substrates. In-situ calibration of the growth temperature allows for a systematic variation with unprecedented resolution. Characterization by photoluminescence (PL) indicates that, at low growth temperatures, nanowires grown on (1 1 1)B substrates incorporate higher density of defects than wires on (1 0 0). On either substrate, nanowire core growth temperatures above 450 °C result in rising defect luminescence in the PL spectra concomitant with the increased epitaxial growth on the nanowire sidewalls at these higher temperatures. This work presents a systematic study of nanowire growth conditions that reveals the correlation between the growth temperature of the GaAs core, the chosen substrate surface orientation, and the resulting optical properties of GaAs/AlGaAs nanowires.