The Growth And Properties Of Semiconducting Multi-components Oxide Thin Films

Semiconducting multi-component oxide is a kind of typical semiconductor material, it has a wide range optical band gap, high melting point and high transtarency at visible light range in general. Make it can be applied to a variety of electronic devices. Such as solar energy transparent conductive electrode, liquid crystal display and uv detector, etc. as the pixels switch and driving element in liquid crystal display fields, the thin film transistors play a very important role. Therefore, in this paper, we aimed at amorphous ZnSnO3 and amorphous ZnGeO3 oxide thin films. using the molecular beam epitaxy, exploring their properties. the amorphous ZnSnO3 thin film transistor was prepared. On this basis, we developed ZnSnO3/ZnGeO3 heterostructure thin film transistor and explored the photoelectric properties preliminarily. The specific content and the conclusion is as follows:1. The ZnSnO3 thin films were prepared using the molecular beam epitaxy. radio frequency power was studied on the surface morphology and optical properties of the thin films. The results show that ZnSn O3 was amorphous, with the increasing of oxygen ions and energy, the ZnSnO3 thin films became smooth and density. Visible light transmission tests indicate that when the radio frequency power greater than 200 W, the films show a sharp absorption peak in the 250 nm to 350 nm wavelength band. the average transmission is about 80%. the optical band gap is about 3.41 eV with calculation, XPS tests show that the ZnSnO3 thin films exists a certain proportion of oxygen vacancy.2. With the optimized preparation process, the ZnSnO3 thin film transistor was prepared. the tests and calculation results show that W/L=80 μm/13 μm thin film transistor threshold voltage is 5 V, the electron mobility is about 6.35×10-3 cm2·V-1·s-1. threshold swing is 25 V/decade, switch current ratio is 38. It suggests that the reasons of low electron mobility are: first, there is a certain proportion of oxygen vacancies in ZnSnO3 films, oxygen vacancies are positively charged, lead to capture carriers. second, the boundary defect with ZnSnO3 film and SiO2 film was significant, carriers are captured by the boundary defects possibly.3. The ZnGeO3 thin films were prepared using the molecular beam epitaxy. The related results show that the ZnGeO3 thin films was amorphous, the film surface is flat and level density, the average transmittance is about 90% in the visible light band. the calculation for optical band gap is about 4.1eV, XPS tests show that the oxygen vacancies was existed in ZnGe O3 film, and it cannot be ignored.4. The feasibility of amorphous ZnSnO3/ZnGeO3 heterojunction thin film transistors was explored. The related tests show that W/L=80 μm/13 μm thin film transistor threshold voltage is-10 V, the electron mobility is about 0.06 cm2·V-1·s-1. the threshold swing is 33 V/decade, switch current ratio is 40. W/L=80μm/3 μm thin film transistor threshold voltage is-14 V, the electron mobility is about 0.05 cm2·V-1·s-1. the threshold swing is 28 V/decade, switch current ratio is 44. Compared to ZnSnO3 thin film transistor, the electron mobility of ZnSnO3/ZnGeO3 heterojunction thin film transistor has raised substantially. At the same time, the threshold voltage is left shift. it shows that amorphous ZnSnO3/ZnGeO3 heterojunction thin film transistor has been effectively improved, it laid a certain foundation for next to develop the better performance of amorphous heterojunction thin film transistor.5. The ultraviolet reponse tests for ZnSnO3/ZnGeO3 heterojunction thin film transistor show that light current significantly. The material is sensitive to ultraviolet. But, along with ultraviolet light, the current control ability for gate voltage to channel current is abated, the transistor characteristics of the device is degraded.