Study On TiO₂ Ultraviolet Photoconductive Detector

Ultraviolet (UV) detectors have been much studied for these recent years because of its important application in the very many fields. The Ge-based and Si-based UV detectors have been into the commercial application, especially Si-based UV detectors for its mature technologic level. Further UV detectors based the alloy with Ge and Si have been succeed to be manufactured. And the UV detectors based GaAs and GaP and their alloy have been also researched much, and it makes lots progresses in the study about them. In recent years, UV detectors have been developed quickly with the development of the preparation method on the material. The UV detectors based on the wide-band semiconductors have been important focus of attention in the last decade. The most study among them is on the GaN-based UV detector, and have most progress. Besides it, ZnO, SiC, diamond are studied very much too. But the progresses about them are not as much as GaN due to some disadvantages. For example, the quality of the materials is not good as the GaN's, and the preparation technology is not very mature.TiO₂ is a kind of wide-band semiconductor. It not only has very good physics and chemical property, but also has good optics property. In recent years, TiO₂ has been researched on the fields as gas or moistness sensor and photocatalyst and solar cell. It has already become the focus of the domestic and international relevant fields. The bandgap of TiO₂ is 3.0eV³.2eV, which make it very attractive for the UV detector.In this paper, we present the fabrication of the metal-semiconductor-metal (MSM) structured photoconductive detector based TiO₂ thin film. First of all, we discuss the classification of the UV detectors, especially of the semiconductor UV detectors. After classification we make a deep analysis and discussion about the operation principle andmain parameter of the semiconductor UV detectors, especially of the photoconductive detector.After the theory analysis, we carry on research to the property of the TiO2 thin film under different anneal temperatures through various kinds of characterization technique. From these, we find out the rule about the change of its structure and optics property with the change of anneal temperature, then choose the suitable condition to prepare the TiCh thin film which accords with the requirement. We prepare nanometer crystal TiO2 thin film by Sol-Gel. Through X-ray diffraction(XRD), we can find out nanometer crystal exist as anatase when temperature is 350-75CTC, while nanometer crystal exist as both anatase and rutile when temperature rises to 850°C. Through atomic force microscope (AFM), we can find out the size of the crystalline is bigger and bigger, and the quality of the crystal is better and better when the anneal temperature gets higher and higher. Through X-ray photoelectron energy spectrum (XPS), we can find out lattice oxygen and absorption oxygen exist on the surface of the TiO2 thin film, which means a large number of oxygen vacancies exist. We also measure the absorption characteristic in the ultraviolet light of samples with the anneal temperature 650°C,750°C,850°C respectively. We can find out each sample has strong absorption in the ultraviolet light range and hardly absorbing in visible light range. The absorption edge of the spectrum has red-shift phenomenon with the anneal temperature rising.Then, we fabricate MSM structured photoconductive UV detector based TiO2 thin film. We sputter a thin Al film on the surface of the TiC>2 thin film with radio frequency magnetism sputter, and the contact between Al and TiC>2 is ohmic contact. Then we make Al film to be interdigitated electrode with standard photolithography technology. We have done some tests to the photocurrent characteristics of TiO2 detector, and made discussion. Through the spectral responsivity, which is about the relationship between the photocurrent of the detector and incident light...