Comparison of Electrical Properties and Bias Stability of Double-Gate a-HIZO TFTs According to TFT Structure

We fabricated two types of double-gate amorphous hafnium-indium-zinc oxide thin-film transistors: a back-channel etch (BCE) type and an etch stopper (ES) type. The normalized on-current and field-effect mobility of the BCE type are larger than those of the ES type. Furthermore, when applied with a positive bias stress, stability trends compared for each single-gate device are different according to structures. We suggest that the reason for the different electrical properties and bias stability originates from the ES structure in which some regions under the source/drain electrodes block the top-gate field; thus, there is no carrier accumulation or charge trapping into the dielectric layer.