Ultrathin-Film Transistors Based on Ultrathin Amorphous InZnO Films

Ultrathin amorphous InZnO ( ${a}$ -IZO) films and the corresponding ultrathin-film transistors (UTFTs) have been prepared by pulsed laser deposition (PLD) for the first time here. With ultrathin amorphous ZnSnO ( ${a}$ -ZTO) films and the related UTFTs as a comparison, the properties of ultrathin a-IZO films and behaviors of the corresponding UTFTs were studied in detail. Also, we have taken a new approach to compare the content of oxygen vacancies ( ${V}_{\textit {O}}$ ) in amorphous oxide semiconductors (AOSs) of different systems, which explains their different properties and behaviors well. The thickness of the ultrathin a-IZO film is approximately 3.1 nm. Compared to ultrathin a-ZTO films, ultrathin a-IZO films depict lower ${V}_{O}$ content and lower carrier concentration. In addition, ultrathin ${a}$ -IZO films display very high transmittance over 95% in the visible region. Furthermore, a-IZO UTFTs exhibit better performance than a-ZTO UTFT, such as a lower off-current of 3.3 $\times \,\,10^{-10}$ A, a larger ${I} _{ \mathrm{\scriptscriptstyle ON}}/{I} _{ \mathrm{\scriptscriptstyle OFF}}$ ratio of $1.5\times 10^{7}$ , a larger $\mu _{\text {sat}}$ of 20.7 cm $^{2}\,\,{V} ^{-1}\,\,{s} ^{-1}$ , a smaller ${V} _{\text {th}}$ of 1.2 V (operating in the enhancement mode), a lower subthreshold swing (SS) of 0.303 V/decade, and a lower ${N} _{t}$ of $8.9\times 10^{11}$ cm−2. Meanwhile, the long-term stability of a-IZO UTFT is similar to a-ZTO UTFT. Above all, a-IZO UTFTs exhibit excellent performance and may be a promising candidate for future displays.