Solution-processed amorphous hafnium-lanthanum oxide gate insulator for oxide thin-film transistors

Abstract

Solution-processed high-K dielectrics for oxide thin-film transistors (TFTs) have been widely studied with the objective of achieving high performance and low-cost TFTs for next-generation displays. In this study, we introduce an amorphous hafnium-lanthanum oxide (HfLaO_x) gate insulator with high electrical permittivity which was fabricated by the simple spin-coating method. In particular, the solution-processed HfLaO_x dielectric layer, which was achieved by a mixture of two Hf and La metal hydroxide precursors, showed amorphous properties, a low leakage current and a high dielectric constant. The solution-processed HfLaO_x dielectric layers showed a breakdown voltage as high as 5 MV cm⁻¹ in strength and a dielectric constant above 22. Based on their implementation as a gate insulator, the solution-processed ZnO/HfLaO_x TFTs showed good and stable performances during operation at a low voltage. A mobility of μ = 1.6 cm² V⁻¹ s⁻¹, an on/off current ratio of 10⁶, and a threshold voltage of 0.0015 V were obtained under a 5 V gate bias. Our results show the possibility of the solution-processed amorphous HfLaO_x dielectric layer as a gate insulator for oxide TFTs. We believe that this amorphous HfLaO_x dielectric has good potential for next-generation high-performance TFT devices.