Bandgap Engineering in Wurtzite GaAs Nanowires by Hydrostatic Pressure

Band structure of wurtzite (WZ) GaAs nanowires (NWs) is investigated by using photoluminescence measurements under hydrostatic pressure at 6 K. We demonstrate that WZ GaAs NWs have a direct bandgap transition with an emission energy of 1.53 eV, corresponding to the optical transition between conduction band Γ_7C and valence band Γ_9V in WZ GaAs. The direct-to-pseudodirect bandgap transition can be observed by applying a pressure approximately above 2.5 GPa.