Optical And Electrical Properties Of Zinc Oxide Thin Films

ZnO is a semiconductor material with a wide band-gap of 3.37eV and a high exciton binding energy of 60meV at room temperature. Recently, it was considered to be a new photo-electric material in shortwave length as GaN. In 1996, stimulated UV emission of ZnO at room temperature was reported, and ZnO as a UV laser material attracted people's attention immediately. There are two crucial difficulties for ZnO shortwave light emitter applications need to be solved. One is that the reliable and reproducible technique to grow high quality p-type ZnO is not found yet. Another is that the intensity of UV emission from ZnO film is not strong enough.The hetero-epitaxy of ZnO film is also an important work. Si is a nice substrate because of its low cost. However, to grow higher crystal quality ZnO films on Si substrate is rather difficult because of the mismatch between ZnO and Si.ZnO is a semiconductor material with photo-voltage property. It is a potential candidate of solar cells. It also can be applied to UV detectors because of its wide band-gap.Considering these research background, the contents of the dissertation are listed as follows:Firstly, the electrical and optical properties of Ag-doped ZnO were studied. Ag-doped ZnO was found to be a potential p-type semiconductor material. Furthermore, novel enhancement of ultraviolet emission of Ag-doped ZnO was observed due to Ag₂O nanoclusters formatted during Ag doping.Secondly, the epitaxy parameters of the ZnO films on Si substrates using ratio-frequency magnetron sputtering were studied for growing higher crystal quality ZnO. The deep level centers in ZnO films on Si substrates were also studied. SiC and Al₂O₃ buffer layers were applied to prepare better ZnO films on Si substrates. The results showed that both the two type of buffer layers can improve the crystal quality of ZnO films on Si substrates. Moreover, Al₂O₃ buffer layer can increase the thickness of ZnO films.Lastly, the photo-voltage property of ZnO film was studied. ZnO films also showed a sensitive ultraviolet response because of its wide band-gap. Based on these results, primitive ZnO ultraviolet detectors was successfully prepared.