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

Abstract

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 cm(2)/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. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4721519]