Characteristics of al doped ZnO films prepared on polyethylene terephthalate substrate by unbalanced magnetron sputtering method for organic thin film transistors

Aluminum-doped ZnO (AZO) thin-films were deposited on PET flexible substrates at the room temperature by an unbalanced magnetron sputtering (UBMS) method with 2 wt% Al₂O₃ doped ZnO target. The effect of pulsed DC power with frequency on the electrical, optical, and structural properties of the AZO films for the application of organic thin film transistors were investigated. The AZO films were deposited with various pulse DC powers with frequency at room temperature. The AZO films prepared by UBMS exhibited low resistivity, high crystallinity and uniform surface morphology. The AZO thin films deposited on PET substrate exhibited higher average optical transmittance of 90% in visible range between 500 to 550 nm wavelengths with various pulse frequencies. Also, we fabricated the organic thin film transistors (OTFTs) of the bottom gate structure using AZO gate electrodes, and we estimated the device performance of the OTFTs including I_D-V_D, I_D-V_G, threshold voltage V_T, on/off ratio and field effect mobility.