Effects of Carrier Concentration, Indium Content, and Crystallinity on the Electrical Properties of Indium-Tin-Zinc-Oxide Thin-Film Transistors

We report the effects of carrier concentration (NCH), indium (In) content, and crystallinity (X
_c
) on the electrical properties of indium-tin-zinc-oxide (ITZO) thin-film transistors (TFTs). The ITZO TFT with the lowest NCH, In content, and amorphous phase at the optimized oxygen flow rate has high field-effect mobility a (μ
_FE
) of 37.2 cm
²
/V·s, high ON/OFF current ratio (I
_ON
/I
_OFF
) of ~ 1×10
⁷
, and low subthreshold swing (S.S) of 0.93. With increasing NCH, In content, and X
_c
, μ
_FE
, I
_ON
/I
_OFF
, and S.S surprisingly degraded to 14.4 cm
²
/V·s, ~ 4×10
⁴
, and 4.01, respectively. Our high ITZO TFTs with μ
_FE
of 37.2 cm
²
/V·s, obtained thorough control of the N
_CH
, In content, and X
_c
, was suitable for application to next generation ultrahigh resolution displays as well as high frame rate displays.