Oxygen Content and Bias Influence on Amorphous InGaZnO TFT-Based Temperature Sensor Performance

A temperature (
${T}$
) sensor based on an amorphous InGaZnO (a-IGZO) thin-film transistor (TFT) is demonstrated and its performance is analyzed quantitatively. The performance analysis includes the influences of the gate-to-source bias (
${V}_{{GS}}$
) and oxygen content in IGZO on the mobility (
$\mu $
), threshold voltage (
${V}_{T}$
), and drain-to-source current (
${I}_{\text {DS}}$
) of TFTs. The linearity and sensitivity of the sensor are found to improve with decreasing oxygen content and increasing
${V}_{\text {GS}}$
, because
$\partial {I}_{\text {DS}}/\partial {T}$
is quantitatively dominated by
$\mu $
and (
${V}_{\text {GS}} -{V}_{\text {T}}$
) rather than by
$\partial \mu /\partial {T}$
and
$- \partial {V}_{\text {T}}/\partial {T}$
. This indicates that the IGZO TFT has great potential as a temperature sensor in terms of immunity in device/process variation. A sensitivity of 125 nA/K with 1.55 K resolution over a temperature range of 303–373 K was successfully demonstrated in low oxygen and
${V}_{\text {GS}}= {9}$
V conditions.