5.4 Location of interface traps

5.4 Location of interface traps

Interface states are located at the SiSiO2 layer which separates the gate contact from the

conducting channel, which is underneath the gate and between the source and drain region.

5.5 Energy distribution of the interface states

The net charge in the interface states is a function of the position of the Fermi level in the

bandgap[18].

The energy or band gap of silicon is 1.12 eV and generally, acceptor states exist in the

upper half of the bandgap and donor states exist in the lower half of the bandgap.

An acceptor type interface state is neutral if the Fermi level is below the state and

becomes negatively charged if the Fermi level is above the state [18].

A donor type interface state is neutral if the Fermi level is above the state and becomes

positively charged is the Fermi level is below the state [18].

According to the journal by Duval, by using hightemperature conductance spectroscopy,

the Fermi level of the acceptor type interface states was found to be 0.4 eV below the

conduction band of the silicon, while the donor type interface states is 0.38 eV above the

valence band [20].