InGaZnO thin-film transistors with YHfZnO gate insulator by solution process

Created by: Hyun Jae Kim

InGaZnO thin-film transistors with YHfZnO gate insulator by solution process

 Thin‐film transistors (TFTs) with the indium gallium zinc oxide (IGZO) as a channel layer and the yttrium hafnium zinc oxide (YHZO) as a gate insulator layer were fabricated and both of layers were deposited by solution process. YHZO solution was prepared by dissolving yttrium nitrate, hafnium chloride, and zinc acetate into 2‐methoxyethanol with additional stabilizers. The spin coating and annealing procedures were repeated several times to obtain sufficient thickness for gate insulator in IGZO TFTs. The electrical characteristics of YHZO films were analyzed by capacitance–voltage and leakage current measurements. The dielectric constant was about 16.4 and leakage current density was about 6 × 10−8 A/cm2. In solution-processed IGZO TFTs with YHZO gate insulator, the field effect mobility, the on‐to‐off current ratio, the threshold voltage, and the subthreshold swing were 0.29 cm2/Vs, ~105, 3.47 V, and 1.26 V/decade, respectively.

DOI: https://doi.org/10.1002/pssa.200983724

 Figure 4 shows the transfer characteristics and the output characteristics of a solution-processed IGZO TFT with YHZO gate insulator. Generally, solution‐processed oxide channel layer behaves as an n‐channel transistor and it has a lot of electron carriers. The high carrier concentration leads to increase of drain current in saturation region according to increase of drain voltage in output characteristics of TFTs. The solution‐processed IGZO TFT with SiNx gate insulator showed increase of drain current as agreeable as this characteristic. However, in this manuscript, the IGZO TFT with YHZO exhibited “hard” saturation of the output characteristics as shown in Fig. 4b. It could be explained that more oxidation generated during the fabrication of IGZO channel on YHZO film. The oxygen in YHZO gate insulator was provided and it led to increase of IGZO film resistivity. Moreover, the gradual decrease of the drain current in the saturation region with increasing drain voltage and the drain voltage shift at which the drain current starts to flow were resulted from gate leakage current. The degree of drain current decrement gradually increased according to increase of gate voltage. It is explained that several electrons start to damage in gate insulator as a leakage current.

Cite this article

Hyun Jae, Kim. InGaZnO thin-film transistors with YHfZnO gate insulator by solution process, Encyclopedia, 2020, v1, Available online: https://encyclopedia.pub/541