Fabrication and Characterization of High-Performance Thin-Film Transistors Based on Epitaxial Ta-Doped TiO2 Films

Ta-doped TiO
₂
(TiO
₂
:Ta) films were synthesized on MgAl
₆
O
₁₀
substrates by the metal-organic chemical vapor deposition (MOCVD) method. The doping uniformities, crystallization qualities, and optical properties of the deposited films were systematically characterized. The measurement results revealed the TiO
₂
:Ta films with low Ta concentrations to be epitaxial anatase films with high transparency in the visible region. Thin-film transistors (TFTs) based on TiO
₂
:Ta films were fabricated. The device with 0.5-at.% Ta-doped TiO
₂
as a channel layer exhibited clear n-type TFT behaviors with a high I
_ON
/I
_OFF
ratio of 4.0 × 10
⁸
, a low subthreshold swing of 0.60 V/decade, and a saturation mobility of 4.4 cm
²
V
^-1
s
^-1
. These parameters were superior to the values of previously reported TiO
₂
-based devices and indicated that the Ta-doped TiO
₂
film was a promising channel material for transparent metal-oxide TFTs.