Physical Internal Gain Mechanisms of ZnO-Based Nanorod Ultraviolet Photodetectors

The structure of the ZnO-based p-ZnO:LiNO₃/ i-ZnO/n-ZnO:In nanorod ultraviolet (UV) photodetectors was grown on sapphire substrates using the vapor cooling condensation system. To study the internal gain mechanisms of the photodetectors, the ZnO-based nanorods were photochemically passivated for different time and operated under various environments to vary the defect density resided on the sidewall surface of the ZnO-based nanorods. The mechanisms of the internal gain, which was attributed to the surface band bending effect of the ZnO-based nanorods induced from the sidewall surface defects and the absorbed oxygen molecules, were thus derived. The specific detectivity of 3.25×10¹⁵ cmHz^1/2W^-1 was obtained for the ZnO-based nanorod UV photodetectors treated with the photoelectrochemical passivation process for 2 min.