III-V nanosttuctures have the potential to revolutionize optoelectronics and energy harvesting. For this to become a reality, critical issues such as reproducibility and sensitivity to defects should be resolved. By discussing the optical properties of molecular beam epitaxy (MBE) grown GaAs nanomembranes we highlight several features that bring them closer to large scale applications. Uncapped membranes exhibit A very high optical quality, expressed by extremely narrow neutral exciton emission, allowing. the-resolution of the more complex excitonic structure for the first time. Capping of the membranes With an AlGaAs :shell results in a strong increase of emission intensity but-ars in a shift and broadening of the exciton peak. This is attributed to,the existence of impurities in the shell, beyond MBE grade quality, showing the high. sensitivity. of these structures to the presence of impurities. Finally,: emission properties are identical at the snbinicron and sulpmillimeter scale, demonstrating the potential of these: structures for large scale applications.