Physical parameters based analytical I-V model of long and short channel a-IGZO TFTs

Abstract

This paper presents an analytical model for amorphous In-Ga-Zn-O thin film transistors based on device physics. The proposed model comprises physical parameters including subgap density-of-states (DOS) and is useful for fabrication process optimization. In addition to delocalized free band states, the model accounts for deep and tail trap states and is valid for complete region of operation. Physical parameters are extracted by employing least square (LSQ) curve-fit function and the model is validated by comparing model outcome with measured characteristics of the device. The proposed model is able to predict the I-V characteristics of the long channel devices to good accuracy. Further, this model is enhanced to predict the behavior of the short channel devices by taking contact voltage drop into account. The model accurately reproduces the measured response of long and short channel oxide TFTs with channel length ranging from 20 μm down to 2 μm with channel width fixed to 20 μm. The average error between measured data and model outcome is found to be < 3 %. The proposed model is useful to design oxide TFT based circuits with different channel lengths using a single set of physical parameters through circuit simulator.