Low-Voltage IGZO TFTs Using Solution-Deposited OTS-Modified Ta2O5 Dielectric

Low-voltage, high-performance thin film transistors (TFTs) that use amorphous metal oxide (MO) semiconductors as the active layer have been getting tremendous attention due to their essential role in future portable electronic-devices and systems. However, reducing the operating voltage of these devices to or below 1 V is a very challenging task because it is very difficult to obtain low threshold voltage (V
_TH
) and small subthreshold swing (SS) MO TFTs. In this article, indium gallium zinc oxide (IGZO) TFTs that use solution-deposited Ta
₂
O
₅
operating at 1 V are demonstrated. To enhance the dielectric properties of the fabricated ultrathin (d ~ 22 nm + 2 nm) tantalum pentoxide films, n-octadecyltrichlorosilane (OTS) self-assembled monolayer (SAM) was used. The morphology and electrical properties of both pristine and OTS-treated Ta
₂
O
₅
films have been studied. The optimized Ta
₂
O
₅
/OTS IGZO TFTs operate at 1 V with saturation field-effect mobility larger than 2.3 cm
²
/V·s, threshold voltage of around 400 mV, SSs below 90 mV/dec, and current ON-OFF ratios well above 10
⁵
. The performance of the presented TFTs is high enough for many commercial applications such as disposable sensors or throwaway, low-end electronics significantly reducing the cost of their production.