A comparative study of characteristics of ZnO TFT for various substrate and fabrication parameters

Several ZnO TFTs (thin-film field-effect transistors) are developed for assessing the characteristics as an FET under different fabrication parameters and substrate materials. These ZnO TFTs are grown using pulsed laser deposition in different substrate temperatures (300-700°C), in different oxygen pressures, and with or without annealing between 400-700°C. The substrates are n-type Silicon with SiO₂ insulating layer, and in some samples, they were accompanied by an additional HfO₂ film layer as a high dielectric material. All the TFTs have bottom-gate structure while the drain, source, and gates are equipped with gold electrodes fabricated by the sputtering method. The films are analyzed by XRD, Raman spectroscopy and photoluminescence as a verification of the presence of ZnO. Using an experimental set-up, the transfer and I-V characteristics are measured whereas the gate voltage is swept over a range of ~10-50 V. To assess the effectiveness of ZnO material for using in a TFT, the field-effect mobility, the drain current density, etc. are measured. Finally, the TFTs are tested for application in high frequency sweeping (1kHz-1MHz) as the hysteresis nature and power gain cut-off frequencies are compared.