Excitonic origin of enhanced luminescence quantum efficiency in MgZnO/ZnO coaxial nanowire heterostructures

The effect of exciton transport on luminescence efficiency was investigated by time-resolved photoluminescence and spatially resolved cathodoluminescence spectroscopy. The internal quantum efficiency of ZnO nanowire (NW) increased from 45% to 56% due to formation of a MgZnO/ZnO coaxial NW heterostructure. MgZnO shell layer formation induced a decrease in the exciton diffusion length and diffusion coefficient from 150 to 120 nm and 9.8 to 6.4 cm2/s, respectively. The change in exciton transport characteristics indicated that exciton transport, in addition to the surface passivation effect, was an important factor determining the luminescence efficiency in the coaxial NW heterostructure.