Effect of annealing temperature of Bi_1:5Zn_1:0Nb_1:5O₇ gate insulator on performance of ZnO based thin film transistors

The bottom-gate structure ZnO based thin film transistors (ZnO-TFTs) using Bi_1:5Zn_1:0Nb_1:5O₇ (BZN) thin films as gate insulator were fabricated on Pt/SiO₂/Si substrate by radio frequency magnetic sputtering. We investigated the effect of annealing temperature at 300, 400, and 500 ^ıC on the performance of BZN thin films and ZnO-TFTs. XRD measurement confirmed that BZN thin films were amorphous in nature. BZN thin films annealed at 400 ^ıC obtain the high capacitance density of 249 nF/cm², high dielectric constant of 71, and low leakage current density of 10-⁷ A/cm² on/off current ratio and field effect mobility of ZnO-TFTs annealed at 400 ^ıC are approximately one order of magnitude and two times, respectively higher than that of ZnO-TFTs annealed at 300 ^ıC. When the annealing temperature is 400 ^ıC, the electrical performance of ZnO-TFTs is enhanced remarkably. Devices obtain a low sub-threshold swing of 470 mV/dec and surface states density of 3.21 X 10¹²cm-².