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5.1.2.6 Effect of the Dielectric Permittivity on the Channel Tunneling

The permittivity of the dielectric layer influences the tunneling current density in two ways: First, the shape of the energy barrier -- and thus the transmission coefficient -- changes. Second, the inversion charge -- and thus the band edge energy -- in the channel is affected. The effect of varying dielectric permittivity is shown in Fig. 5.8. Especially in the low-bias regime, a higher permittivity strongly increases the gate current density.
Figure 5.8: Effect of the dielectric permittivity $ \kappa / \kappa _0$ on electron tunneling current (left) and hole tunneling current (right) in an nMOS (top) and a pMOS (bottom) with 2 nm dielectric thickness, 1e20 cm-3 polysilicon and 5e18 cm-3 substrate doping.
\includegraphics[width=.49\linewidth]{figures/nMosPermittivityElectrons} \includegraphics[width=.49\linewidth]{figures/nMosPermittivityHoles}
\includegraphics[width=.49\linewidth]{figures/pMosPermittivityElectrons} \includegraphics[width=.49\linewidth]{figures/pMosPermittivityHoles}


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A. Gehring: Simulation of Tunneling in Semiconductor Devices