Analysis of the activation energy of the subthreshold current in laser- and solid-phase-crystallized polycrystalline silicon thin-film transistors

Analysis of the thermal and gate-voltage dependences of the current in the subthreshold region is performed on both low-temperature laser-crystallized and solid-phase-crystallized polycrystalline silicon (polysilicon) thin-film transistors (TFTs). Temperature measurements are made at first in order to extract the variations of the activation energy E-A of the drain current with the gate voltage. The plot of the subthreshold current versus the measured activation energy leads to an apparent activation energy E-A/n, where the n factor is extracted from the slope of this plot. The n factor is close to 1 for laser-crystallized polysilicon TFTs while it is rather close to 2 for solid-phase-crystallized ones. These two values can be attributed to a different defect distribution in the two differently crystallized TFTs polysilicon active layers. (C) 2000 American Institute of Physics. [S0003- 6951(00)02830-8].