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

Abstract

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.