Fabrication of ZnO nanowall-network ultraviolet photodetector on Si substrates

ZnO nanowall networks were prepared by plasma-assisted molecular beam epitaxy without a catalyst on Si (111) substrates. The nanostructures have preferred orientation along the c axis. The nanostructures are about 10 to 20 nm thick and about 50 nm tall. The planar geometry photoconductive type metal-semiconductor-metal photodetector based on the ZnO nanowall networks exhibits a high and wide response spectrum, and no decrease from 250 to 360 nm. With the applied bias below 5 V, the dark current was below 6 μA, and the peak responsivity of 15 A/W was achieved at 360 nm. The UV (360 nm) to visible (450 nm) rejection ratio of around two orders could be extracted from the spectra response. (semiconductor devices)