Ultraviolet photodetector arrays assembled by dielectrophoresis of ZnO nanoparticles

Sensitive and fast ultraviolet sensor arrays have been produced by dielectrophoretic assembling of ZnO nanoparticles. The sub-micron device dimensions induce low operating voltage and low power consumption. The devices are long-term stable and operate in air, oxygen and nitrogen. We have determined the absorption and desorption dynamics from the time-resolved photoresponse and conclude that oxygen or carbon dioxide are the photodesorbed species. We could derive the charge carrier concentration and mobility of the device from measurements of the low-bias and high-bias photocurrent. The presence of defects is discussed by comparing electroluminescence spectra from biased devices with photoluminescence spectral maps of ZnO dispersions.