Characteristics of nanostructured CdO/Si heterojunction photodetector synthesized by CBD

In the present work, CdO/Si heterojunction detectors were fabricated by depositing nanostructured CdO film on single crystal silicon wafer by chemical bath deposition (CBD) technique. Films deposition was carried out at different temperatures. To obtain good film stoichiometry heating of films in static air at temperature of 400 °C for 90 min was carried out. The structural properties of CdO films was characterized by X-ray diffraction and atomic force microscope (AFM), these investigations showed that the deposited CdO films have cubic structure. The surface morphology investigation revealed that CdO film is almost homogeneous and consisted of the nanowires with diameter less than 100 nm at temperature of solution 40 °C.The band gap of the films changes from 2.4 to 2.5 eV with increasing preparation temperature. The current–voltage characteristics of photodiodes under dark exhibit good rectification behavior and that ideality factor of heterojunction was found to be in the range of 1.56–3.69 depending on solution temperature. The capacitance–voltage characteristic shows a typical abrupt heterojunction and the built-in-potential was determined. CdO/Si detector has good spectral responsivity in visible and NIR and the maximum responsivity was 0.56 A/W. Rise time of the photodetectors was strongly dependent on solution temperature and the shortest rise time obtained was 45 ns at 2 V.

► AFM images revealed that the grown nanowires CdO with size of 100 nm.
► Ideality factor of CdO/Si heterojunction was found to be in the range of 1.56–3.69.
► Rise time of the photodetectors was strongly dependent on solution temperature.
► The maximum photodetector responsivity was 0.56 A/W at 900 nm.