The total steady-state tunneling current is derived as the sum of the trap-assisted tunneling current (3.122) and the direct tunneling current computed from the TSU-ESAKI formula (3.13)
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(3.149) |
Fig. 3.20 shows the dependence of the gate current density on the
model parameters
(trap energy level) and
for a fixed
phonon energy of
=10meV in an MOS capacitor. For a low trap
energy level traps are located near the conduction band edge in the
dielectric, and direct tunneling prevails. With increasing trap energy level,
the trap-assisted component becomes stronger and exceeds the direct tunneling
current for low bias. The current density shows a peak at low bias which is
due to the alignment of the trap energy level with the cathode conduction band
edge. The HUANG-RHYS factor has only a minor influence on the results, as
shown in the right part of Fig. 3.20.
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A. Gehring: Simulation of Tunneling in Semiconductor Devices