Epitaxial GaAs/AlGaAs core-multishell nanowires with enhanced photoluminescence lifetime.

The modulation of complex GaAs/AlGaAs core-shell nanowire heterostructures by the process of embedding GaAs quantum wells or AlGaAs quantum dots is feasible due to their minor lattice mismatch. In this study, we have grown GaAs/AlGaAs core-multishell nanowire heterostructures by molecular beam epitaxy and investigated their structural and optical characteristics. Our advanced electron microscopy investigations confirmed that we have grown wurtzite-structured GaAs/AlGaAs core-multishell nanowires, in which the AlGaAs inner-shell with a high Al concentration acts as a quantum barrier for the GaAs nanowire core and AlGaAs outer-shell. Photoluminescence measurements show that this unique nanowire heterostructure has a significantly increased carrier lifetime compared to the conventional GaAs/AlGaAs core-shell nanowire heterostructures. The observed prolonged carrier lifetime can be attributed to the increased electron confinement at the core-inner-shell interface and thus the delayed recombination of photoexcited electron-hole pairs. This study provides a possible design of nanowire heterostructures for high-efficiency optoelectronic devices.