A Compact Model of Amorphous InGaZnO TFTs to Predict Temperature-Dependent Characteristics

Abstract

In amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs), the conduction mechanism of percolation and trap-limited conduction prevails within the limits of gate voltage. In these limits, the gate voltage-dependent mobility follows a power law. The temperature dependence of gate-functioned mobility is modeled by introducing very few empirical parameters (P and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> ), where P follows the Arrhenius equation and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> is found to be constant for varying temperature ranges. The proposed model effectively incorporates the combined effects of mobility as a function of temperature and gate voltages of the device using a single formulation for accurate thermal characterization. This model reproduces the measured characteristics of oxide TFT for a wide temperature range with an average error less than 2.5%. The model is implemented in Verilog-A to facilitate circuit simulations. Further, an 11-stage Ring-Oscillator is simulated with the proposed model. These results are compared with the measured circuit response under similar testing conditions to validate the model accuracy in the complete region of operation over a wide range of temperature variations. These simulation results show a good agreement with measured results within 8% accuracy, reinforcing the model validation.