Ordered nanowire array blue/near-UV light emitting diodes.

ZnO-based light emitting diodes (LEDs) have been considered as a potential candidate for the next generation of blue/ near-UV light sources, [ 1 ] due to a direct wide bandgap energy of 3.37 eV, a large exciton binding energy of 60 meV at room temperature, and several other manufacturing advantages of ZnO. [ 2 ] While the pursuit of stable and reproducible p-ZnO is still undergoing, [ 3,4 ] heterojunctions of n-ZnO and p-GaN are employed as an alternative approach in this regard by considering the similar crystallographic and electronic properties of ZnO and GaN. [ 5–7 ] Compared with the thin fi lm/thin fi lm LEDs, [ 5,6 , 8 ] which may suffer from the total internal refl ection, n-ZnO nanowire/p-GaN thin fi lm heterostructures are utilized in order to increase the extraction effi ciency of the LEDs by virtue of the waveguiding properties of the nanowires. [ 9–11 ] But in all of these cases, the n-ZnO nanowires are randomly distributed on the substrate, which largely limits their applications in high performance optoelectronic devices. Here in this work, we demonstrate the capability of controlling the spatial distribution of the blue/near-UV LEDs composed of position controlled arrays of n-ZnO nanowires on a p-GaN thin fi lm substrate. The device was fabricated by a conjunction of low temperature wet chemical methods and electron beam lithography (EBL). The EBL could be replaced by other more convenient patterning techniques, such as photolithography and nanosphere lithography, rendering our technique low cost and capable of scaling up easily. Under forward bias, each single nanowire is a light emitter. By Gaussian deconvolution of the emission spectrum, the origins of the blue/nearUV emission are assigned particularly to three distinct electronhole recombination processes. By virtue of the nanowire/thin fi lm heterostructures, these LEDs give an external quantum effi ciency of 2.5%. This approach has great potential applications in high resolution electronic display, optical interconnect, and high density data storage. The design of the LED is shown in Figure 1a . Ordered ZnO nanowire arrays were grown on p-GaN (Figure 1 b–d), [ 12–14 ]