Recombination-tunneling conduction in Cu- and S-doped ZnO nanorods’ core–shell junction: dependence of diode parameters on thermal annealing temperature and role of interfacial defects

We have investigated the effect of thermal annealing on the diode characteristics of solution-processed novel core–shell coaxial n–p nanorods heterojunction consisting of n-type ZnO as a core and p-type CuS as a shell material. The values of turn-on-voltage, rectification ratio, reverse saturation current density, barrier height, and ideality factors have been improved as the as-prepared heterojunction is annealed at higher temperatures owing to the improvement in the interface between ZnO and CuS as evidenced from the high-resolution transmission electron microscopy. The X-ray diffraction results also confirm the improvement in the crystalline quality of ZnO and CuS through annealing. The experimental current–voltage data are consistent with the presence of dominating recombination-tunneling conduction occurring through the interface defect states between ZnO and CuS. The results demonstrate that an annealing process plays a dominant role in the interfacial defects which helps to modify the diode performance paving a way to cheaper electronic nanodevices.