Zinc oxide interface semiconductor- semiconductor UV photodedectors

In this thesis, undoped ZnO and (ZnO:Alx:My x=%1 at , y=%1, %2, %3, %5 M=Cd, Cu, Mn) co-doped ZnO thin films were prepared by sol gel method to fabricate the metal oxide semiconductor based photodiodes. Undoped and co-doped ZnO thin films were grown on the glass substrates using spin coating method. The absorbance and transmittance of prepared undoped and co-doped ZnO thin films were measured to determine their optical band gaps. Optical band gaps of undoped and co-doped ZnO thin films were calculated via 〖(αhv)〗^(1/n) = A(hv-Eg) equation and the results are discussed and correlated with photodiode performance. The structural properties of the thin films were investigated by X-ray diffraction techniques. The XRD results confirm that the undoped ZnO and co-doped ZnO thin films have the polycrystalline nature. For all the thin films, (002) diffraction peaks are observed in the XRD pattern, showing the preferential growth of ZnO crystallites along c-axis. The typical hexagonal wurtzite structure of thin films is inferred from the XRD pattern. Also the surface images of undoped and co-doped ZnO thin films were taken by SEM. It is apparent from the electron micrographs that morphology of all the thin films has tightly packed grains and relatively smooth surfaces without any voids and crack. The electrical characterization of prepared undoped n-Si/ZnO/Al, co-doped n-Si/ZnO:Alx:My/Al x=%1 at, y=%1, %2, %3, %5 M=Cd and co-doped p-Si/ZnO:Alx:My/Al x=%1 at , y=%1, %2, %3, %5 M=Cu, Mn photodiodes were performed by phototransient current measurements, current-voltage characteristics, capacitance-voltage and conductance-voltage techniques. The electrical parameters and interface properties of the photodiodes were changed with (Alx::My x=%1 at , y=%1, %2, %3, %5 M=Cd, Cu, Mn) dopants content. The photoresponse and rectification properties of undoped n-Si/ZnO/Al, co-doped n-Si/ZnO:Alx:My/Al x=%1 at, y=%1, %2, %3, %5 M=Cd and co-doped p-Si/ZnO:Alx:My/Al x=%1 at , y=%1, %2, %3, %5 M=Cu, Mn photodiodes were changed. It was found that the photoresponse properties of the undoped n-Si/ZnO/Al photodiodes can be improved using various metal dopants. Keywords: Sol-gel, Photodiode, ZnO, Nanostructure, Optical Properties, Semiconductors