Mechanism Analysis of Current–Voltage Characteristic in a Lightly Doped Drain Polycrystalline Silicon Thin-Film Transistor Using Activation Energy

Abstract

We have analyzed the mechanism of the current–voltage characteristic in a lightly doped drain (LDD) polycrystalline silicon (poly-Si) thin-film transistor (TFT) by investigating the activation energy (Ea) in an experiment and the energy band calculated using device simulation. In the off state, Ea decreases as the gate voltage (Vgs) and drain voltage (Vds) increase, which suggests that the off-leakage current is subject to phonon-assisted tunneling with the Poole–Frenkel effect at the junction between the LDD and drain regions. In the subthreshold state, Ea sharply decreases as Vgs increases, which suggests that the subthreshold-transition current is subject to the potential barriers at the junctions between the source, LDD, and channel regions. In the on state, Ea gradually decreases as Vds increases, which suggests that the on current is subject to the potential barriers at the grain boundaries.