High Detectivity Mechanism of ZnO-Based Nanorod Ultraviolet Photodetectors

ZnO nanorod arrays are grown on Mg-doped GaN layer using the vapor cooling condensation system. To suppress the surface states and the dangling bonds residing on the sidewall surface of the ZnO nanorods, photoelectrochemical (PEC) surface passivation is carried out on the ZnO nanorods. The peak photoresponsivity of the unpassivated and the passivated ZnO nanorod photodetectors operating at -5 V was 3.0 × 10³ A/W and 4.6 × 10² A/W, respectively. The PEC treatment dramatically reduces the noise equivalent power level and increased the specific detectivity up to a value of 1.43 × 1015 cmHz^1/2W^-1 Moreover, the noise power density spectra of the ZnO nanorod array photodetectors changed from the dependence of 1/f² to 1/f. These results demonstrate that the generation-recombination centers are successfully passivated by the PEC oxidation method.