Ammonia-free chemically deposited CdS films as active layers in thin film transistors

In this work we have grown CdS thin films using an ammonia-free chemical bath deposition process for the active layer in thin film transistors. The CdS films were deposited substituting sodium citrate for ammonia as the complexing agent. The electrical characterization of the as-deposited CdS-based thin film transistors shows that the field effect mobility and threshold voltage were in the range of 0.12-0.16 cm²V^-1 s^-1 and 8.8-25 V, respectively, depending on the channel length. The device performance was improved considerably after thermal annealing in forming gas at 250 °C for 1 h. The mobility of the annealed devices increased to 4.8-8.8 cm ²V^-1 s^-1 and the threshold voltage decreased to 8.4-12 V. I_on/I_off for the annealed devices was approximately 10⁵-10⁶.