Bias-dependent subthreshold characteristics and interface states in disordered semiconductor thin-film transistors

The sub-threshold characteristics of a disordered thin-film transistor (TFT) are important, where an interface quality and a demarcation between on and off states of the transistor operation are reflected through the sub-threshold slope (SS). Here, we find that the SS associated with the degree of disorder at the film interface appears to be a function of the gate voltage within the sub-threshold regime. In this respect, we provide an accurate physically-based model to explain this gate bias-dependent sub-threshold slope (SS) for amorphous oxide thin-film transistors whereas the conventional model with the constant SS has a huge discrepancy in comparison with the experimental results. For this, we employ a linear distribution of interfacial states rather than the conventional constant model. The proposed model is applied to the measured sub-threshold current-voltage characteristics for different temperatures lower than 300 K, exhibiting a good agreement with each other.