The Fabrication And Study Of Zno-based Thin Film Transistors

Zinc oxide, a kind of semiconductor material with a direct wide band gap (3.37eV at room temperature), has substantial advantages including large exciton binding energy (60meV) and excellent piezoelectric and photoelectric capability, these advantages make it become a focus in photoelectric research field after GaN. ZnO has popular application on civil and military fields, such as ultraviolet detectors, surface acoustic wave device, light-emitting diodes (LEDs), laser diodes (LDs), transparent electrodes.ZnO-based thin-film transistors (TFTs) have attracted much attention because of their particular advantage and potential for replacing Si-based thin-film transistors (TFTs), the conventional TFTs, which has been widely used at present. Meanwhile, since ZnO film is highly transparent in the visible portion of the electromagnetic spectrum, therefore, transparent thin film transistors (TTFT) can be fabricated when adopting ZnO, transparent substrate, and other transparent materials including insulator material, electrode material, etc. and this is especially important in display and transparent electronics fields. Related research is doing popularly domestically and internationally, and it becomes a research hotspot in this filed.The main work of this paper is as follows:1. Applying two methods of Metal Organic Chemical Vapor Deposition (MOCVD) and Radio Frequency (RF) Sputtering, high-quality ZnO thin film were deposited on glass substrates by optimizing processing technology. We optimized the growing temperature, did some research on the effect of oxygen flow on the growth and quality of ZnO thin film, as well as tested and analyzed the related characteristics by the methods of X-ray diffraction(XRD), Photoluminescence (PL),Atomic force microscopy(AFM) ,HALL and optical transmission spectra.2. On the basis of the ZnO thin film material, we designed and fabricated successfully ZnO-TFT. ZnO-TFT photolithography patterns on different structures are designed, the temperature, exposure time, and exposure intensity, and related processing conditions and operation are optimized in the process of lithography, and the performance of the devices has been tested and analyzed. The device we fabricated is bottom-gate ZnO-TFT, and the current on/off ratio is to be 106. In addition, the transistor has high optical transparency (～80% for wavelength >380 nm).