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
_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 ×10
^-10
A, a larger I
_ON
// OFF ratio of 1.5×10
⁷
, a larger u
_sat
of 20.7 cm
²
V
^-1
s
^-1
, a smaller V
_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 × 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.