R-G Centers/Traps

Deep Energy level

Impurity Atoms allowed energy levels in the midgap region.

Crystal defects deep level states

from CB and hole from VB comes to the RG center and gets annihilated. It can also be the considered on capture of having one electron from CB to deep state and then the same electron can jump to VB canceling a

RG recombination non radioactive

Heat/lattice vibration produced

Fig. 8.6

Fig. 8.7

Dominant mechanism in G- R in semiconductors.

rate of change of electron concentration due to RG recombination + generation

rate of change of holes

No of R-G traps/cm 3 filled with

No of R-G traps/cm 3 empty.

Total no of traps or RG centers per cm 3 .

A mechanism in trap recombination or generation.

Electron capture

no. of electrons to be captured empty trap states.

more captured n

Constant.

The probability that the recombination-generation center is occupied by an electron

-ve sign to indicate that electron capture acts to reduce the no. of electrons in CB

units of cm 3 /sec.

= thermal velocity capture cross section.