Drift-diffusion analysis of current crowding mechanism: Current-dependent series resistance

The current crowding mechanism is crucial in the modeling of the series resistance in staggered thin-film transistors, giving the first idea about the current distribution at the overlap region. However, the model for this mechanism neglects the diffusion phenomenon and is limited to small drain-voltage condition. In this paper, by using theoretical analysis and simulations, we introduce a drift-diffusion approach into the interpretation of the current crowding mechanism, pointing out the dependence of the series resistance not only on the gate-voltage but also on the current magnitude. In addition, we compare the series resistance at the source and at the drain, remarking the origin of their difference.