Optical and Electrical Characterization of (002)-Preferentially Oriented n-ZnO/p-Si Heterostructure

In this paper, preferentially oriented (002) ZnO thin films have been grown on Si (100) and glass substrates using radio frequency magnetron sputtering. The dependence of the quality of the ZnO thin films at different substrate temperatures on the growth is studied. A ZnO thin film with c-axis-oriented würtzite structure is obtained at a growth temperature from 200 to 400 C. X-ray diffraction shows that the full width at half maximum θ2θ of (002) ZnO/Si is located at approximately 34.42◦, which is used to infer the grain size that is found to be 17 nm to 19.7 nm. The FWHM is 9.5 ◦ to 8 ◦ in rocking curve mode, from which the crystalline quality has been determined. The texture degree demonstrates the improvement in quality with the increase of substrate temperature, which is best at 400 C. The band gap extracted by UV transmittance spectrum has been identified as 3.2 eV at 400 C. The electrical characteristics via CV and IV measurements on the basis of the heterojunction thermal emission model confirm the domination of high-density grain boundary layer existing at the interface. The transport currents indicate to the presence of space-charge-limited current and trap-charge-limited current mechanisms