Polarity-controlled ultraviolet/visible light ZnO nanorods/p-Si photodetector

Vertically aligned ZnO nanorods of high quality were grown on p-type silicon substrate by a modified chemical vapor phase process. Low temperature photoluminescence measurements show a near band gap donor bound exciton full width at half maximum of less than 500 μeV, and only weak green defect luminescence proofing the superior optical quality of the ZnO structures. n-ZnO/p-Si photodetector devices were processed from these upright standing nanorods. The devices show bias dependent selective photon response: under forward bias, an ultraviolet to visible sensitivity ratio of three orders of magnitude was achieved, while under reverse bias ultraviolet and visible light contributed similarly to the electrical readout current. Thus, the characteristics of this detector element can be switched between "solar blind" and "broadband."