In Semiconductor Physics
In semiconductor physics, this equation is called the drift–diffusion equation. The word "drift" is related to drift current and drift velocity. The equation is normally written:
where
- n and p are the concentrations (densities) of electrons and holes, respectively,
- q>0 is the elementary charge,
- Jn and Jp are the electric currents due to electrons and holes respectively,
- Jn/-q and Jp/q are the corresponding "particle currents" of electrons and holes respectively,
- R represents carrier generation and recombination (R>0 for generation of electron-hole pairs, R<0 for recombination.)
- E is the electric field vector
- and are electron and hole mobility.
The diffusion coefficient and mobility are related by the Einstein relation as above:
where kB is Boltzmann constant and T is absolute temperature. The drift current and diffusion current refer separately to the two terms in the expressions for J, i.e.:
Read more about this topic: Convection–diffusion Equation
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