Dependence of off-leakage current on channel film quality in poly-Si thin-film transistors and analysis using device simulation

The dependence of off-leakage current on channel film quality in poly-Si thin-film transistors has been analyzed using two-dimensional device simulation. It is found that the off-leakage current decreases as the intragrain trap density decreases for the low V_gs. This is because the Phonon-assisted tunneling with Poole-Frenkel effect is the dominant mechanism of the carrier generation and the generation rate of carrier pair decreases as the intragrain trap density decreases. On the other hand, the off-leakage current slightly increases as the intragrain trap density decreases for the high V_gs. This is because the band-to-band tunneling is the dominant mechanism and the influence of the intragrain trap density to the carrier conductance is larger than that to the generation rate.