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| 8.8 Surface States and Interface Trapped Charge |
| At Si-SiO2 interface, the lattice of bulk silicon and all the properties associated with its periodicity terminate. As a result, localized states with energy in the forbidden energy gap of silicon are introduced at or very near to the Si-SiO2 interface. Interface trapped charges are electrons or holes trapped in these states. The probability of occupation of a surface state by an electron or by a hole is determined by the surface state energy relative to the Fermi level. An electron in conduction band can contribute readily to electrical conduction current while an interface trapped electron does not, except hopping among the surface states. Thus by trapping electrons and holes, surface states can reduce conduction current in MOSFETs. |
| Surface states can also act as localized generation-recombination centers and lead to leakage currents. |
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| 8.9 Conclusion |
| Because short channel effects complicate device operation and degrade device performance, these effects should be eliminated or minimized, so that a physical short channel device can preserve the electrical long channel behaviour. |
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