Effect of the interfacial (low-k SiO2 vs high-k Al2O3) dielectrics on the electrical performance of a-ITZO TFT

In this work, the effect of an interfacial low-k dielectric layer such as -SiO2 was suggested along with the effect of an interfacial high-k dielectric layer such as -Al2O3 on the electrical characteristics and then the electrical properties of the a-ITZO TFT such as the equivalent oxide thickness (EOT) of gate dielectric, gate capacitance per unit area (C-i), on-current (I-on), on-off current (I-on/I-off) ratio and field-effect mobility (mu(FE)) of the a-ITZO TFT. The main purpose of this study is to conduct a comparative study to highlight the impact of the interfacial high-k dielectrics such as -Al2O3, compared to low-k -SiO2, the existing between the a-ITZO active layer and high-k -Hfv layer in a-ITZO TFT based on the double-layered dielectric. Therefore, the several analyses were implemented through numerical simulation of the device by the Silvaco TCAD Atlas software that was used to carry out a detailed numerical analysis for investigating the relationship between different types of the interfacial (low-k and high-k) dielectric oxides and the performance of a-ITZO TFT. The results showed that TFT based on the double-layered dielectric -(Al2O3/HfO2) with a physical thickness (PT = 30 nm) it can provide good electrical properties (EOT = 6.33 nm, C-i = 5.45 x 10(-7) F cm(-2), I-on = 1.61 x 10(-5) A, I-on/I-off = 1.56 x 10(9) and mu(FE) = 24.11 cm(2) V-1 s(-1)) better than the properties provided by TFT based on the double-layered dielectric -(SiO2/HfO2) for the same physical thickness (EOT = 12.23 nm, C-i = 2.82 x 10(-7) F cm(-2), I-on = 8.54 x 10(-6) A, I-on/I-off = 8.27 x 10(8) and m(-2) = 29.31 cm(2) V-1 s(-1)). However, we cannot neglect the fundamental role of the interfacial low-k -SiO2 layer between the channel and the high-k dielectric, which has some beneficial qualities with regard to the carrier mobility in the transistor channel. In addition, although there is a difference in the value of leakage between the two devices, its effect is very poor on the performance of the device and its reliability, especially for low gate tensions.