Processes at the Bottom Level:



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Processes at the Bottom Level:

It is assumed that three processes occur at the bottom level : hole capture, hole emission and electron emission. The electron capture vanishes when the bottom level is low so that .

a)
hole emission versus hole capture

 

With benefit of , one obtains . The traps above the Fermi level capture holes with a much larger probability than they emit the holes. The hole emission can be considered as vanishing in this interval.

b)
hole emission versus bottom level duration

 

 

For the levels above the hole emission can be neglected during .
The lower boundary of the energy interval which is active in charge pumping is given by

 

The Fermi level governs the lower boundary when

 

which corresponds to the cases when is lower than the charge-pumping flat-band potential .

c)
capture of holes versus emission of electrons

 

 

The hole capture is faster than the electron emission for all energy levels below and vice versa. An interesting relationship holds: . If the gate bottom level drives the interface into strong accumulation, holds and it follows that . In the later case the electron emission is negligible during the capture of holes at the bottom level.

d)
electron emission versus bottom-level duration

 

The traps above the level are emptied during by the electron emission. The emission is very fast for all traps, except for the traps around the level . As a consequence, the traps above this level are not available for hole capturing during , when the hole capture has a low probability. Regarding c) and d) the upper boundary of the energy interval available for the hole capture is determined by

 

According to the preceding discussion, at the end of the bottom level



next up previous contents
Next: Charge-Pumping Current Up: 3.3.1 Rigorous Analysis of Previous: Processes at the



Martin Stiftinger
Sat Oct 15 22:05:10 MET 1994